This is very complicated. When I was young and didn't know what sex was, I experimented with a boy. Before that, when I was very, very young I experimented with my adult female cousin. I had no idea what I was doing.
I was so upset that it haunted me for a really long time. Eventually I twisted it in my mind that the boy had done it to me, and I didn't want him to because I had no idea how to deal with it. I lied to myself that I had been raped because I didn't want to accept and take responsibility for my own stupid actions, so I accused someone else of a horrible thing.
Several years later I told my parents that I had been raped. This was a very long time ago. I guess I wanted to pretend I hadn't done anything, but I still wanted to get over the trauma by talking to someone. I didn't say anything until after I hadn't seen the boy for a long while, so the boy was not affected by my accusation. He doesn't know what I had falsely accused him of and my parents don't talk to him. I never told them about my cousin, though, because it would cause a tear in our family.
After I told this lie, I regretted telling it and wished I had a time machine to not tell it. I kept trying to repent of it, but can I really repent of a lie that I won't admit I lied about? Am I not still lying? If my mom asked me, "Did you lie about that?" I would admit I lied. But if my dad asked me, I don't think I would admit it. Therefore, I'm thinking either I just don't tell anymore lies other than this one and "repent," but is that true repentance? Or I do tell them, but I wait until I move out of the house so they can have some time to process it properly and not have to see my idiot face every day after they realize what an awful thing I did to them to cause them so much pain with a lie. But can I not repent until then because I have not admitted to the lie yet?
But what if after I admit I lied about such a thing, my mom hates me? I love her so much and she's my best friend. I don't want her to hate me. I don't want to ruin my relationship with her. If I admit to her I lied about this, won't I be hurting her twice? At this point wouldn't she rather believe I had been raped, than that I lied about it? But I can't go on with this -- I can't -- it's sickening, it is consuming me, it's haunting me, I hate myself. I feel inferior to everyone around me because of this lie. I feel I am an evil person, which everyone is, but I mean I am more evil than everyone else.
What do I do? Can I not go to heaven until I admit the truth? Because it says in the Bible that you must repent of your sins to be forgiven, and you must be forgiven to go to heaven. But can you repent of a lie if you don't admit you lied?
Let me see if I can't put things back into their proper perspectives.
First, while you didn't not know what you were doing when you sexually played around with your adult cousin, she did know what was going on. Given the difference in ages, that is called statutory rape -- in other words, it is defined as rape regardless of whether you agreed to sexual acts or not. In other words, you were sexually abused by an adult. You did not "experiment" with her because you did not even know what it was at the time. You haven't been honest with yourself about what happened.
It is not unusual for a child who was sexually abused to act out. The form of acting out varies widely, but it results from the dilemma that arises from knowing you willing did something wrong and enjoyed it. Because it is you, you don't give yourself the honest assessment that as a child it is the adult's responsibility. In fact, most abusers get the child to accept responsibility for what the abuser done, knowing that the guilt will keep the child from telling anyone what happened. Your cousin did an effective job manipulating you in this respect. You still see yourself as responsible for what happened. You chose the route to repeat what was done before but this time with a male instead of a female.
At this point in your story, I don't know information. I don't know if the boy was your age or not. Whether the two of your were sexually developed -- though I suspect that you were. My guess at the moment is that you initiated the encounter and he willingly accepted the chance to have sex. Assuming that both of you were young teenagers, then you two got involved in fornication.
Later, you wanted to talk with someone about the sins, but you didn't want to accuse your cousin, so you combined the two and claimed that the boy raped you. While you claim that no harm was done, the truth is that you ruined another person's reputation in order to make yourself look better and to protect your cousin who molested you. You don't know what the consequences of those accusations will be in the future.
"When I kept silent about my sin, my body wasted away through my groaning all day long. For day and night Your hand was heavy upon me; my vitality was drained away as with the fever heat of summer. I acknowledged my sin to You, and my iniquity I did not hide; I said, "I will confess my transgressions to the LORD"; and You forgave the guilt of my sin" (Psalms 32:3-5).
The first step in turning this around is to be honest with yourself about what happened. You might need to discuss this with someone who can give you a more neutral view about the events and who was responsible for them. Then you need to approach God and admit where you sinned, especially about the lies you have been telling yourself and others (I John 1:9).
The second step is to do something about them to show you've changed. "For the sorrow that is according to the will of God produces a repentance without regret, leading to salvation, but the sorrow of the world produces death. For behold what earnestness this very thing, this godly sorrow, has produced in you: what vindication of yourselves, what indignation, what fear, what longing, what zeal, what avenging of wrong! In everything you demonstrated yourselves to be innocent in the matter" (II Corinthians 7:10-11). The past can't be undone, but you can fix a bit of the damage you've done. It will require humility on your part -- a willingness to be seen as less than who you are so that others may be better.
One of the things that is holding you back is your pride, but another is your fear. You imagine how your parents will respond, so you've already decided how everything will play out. But it is nothing more than your imagination, which most likely will be wrong. You don't know how they will respond. What you fear is not reality but your own vivid imagination.
Tell your mother the truth. Start from the beginning. Tell her what your cousin did with you. Tell her what you did with this boy. Tell her about how hard it was to sort through all your emotions and how you lied about the boy raping you. If you have difficulty talking about this verbally, then write it out so you can shape the words to be accurate. If you do choose to write it, then leave out all the emotional words. Just state what happened as objectively as you can and as fairly as you can. Then at the end, tell your mother that you are sorry for misleading her.
If you are going to change, the best time to do it is now. Waiting gains you nothing and risks you not being able to make any changes because the future is not guaranteed. "Yet you do not know what your life will be like tomorrow. You are just a vapor that appears for a little while and then vanishes away. Instead, you ought to say, "If the Lord wills, we will live and also do this or that." But as it is, you boast in your arrogance; all such boasting is evil. Therefore, to one who knows the right thing to do and does not do it, to him it is sin" (James 4:14-17).