I met a boy who is an Adventist. We became good friends. Slowly I started to talk to him on phone and studied the Bible together with him over the phone. Eventually we started to meet each other and study the Bible together. Then we began meeting in parks and spending time together. Over time it changed into meeting alone and in secret places hiding from others, along with hugging each other to say hello or to say bye. Eventually it changed into kissing and slowly evolved into having sex, though we called it love. As time went by, whenever we met we had a sex and we said it's love. He calls me to have that stupid love once a month.
I feel as if I have ruined my life. The only way seems to me is to end my life. But I found a friend. Whenever I talk to him I feel as if he is leading me toward Christ. I want to get married to the second friend, but I fear my the past. Should I tell him about the past or should I hide it from him? Or should I marry the first friend, but when I am with first friend I feel I am going astray from God.
Calling sex "love" is just a way to lie to yourselves about the sin you are committing. You are not married, so sex outside of marriage is fornication. "Marriage is honorable among all, and the bed undefiled; but fornicators and adulterers God will judge" (Hebrews 13:4). You and he are pretending to be followers of Christ while living a life that is contrary to what Christ stands for. "Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived; neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor homosexuals, nor thieves, nor the covetous, nor drunkards, nor revilers, nor swindlers, will inherit the kingdom of God" (I Corinthians 6:9-10).
The first point that needs to be addressed is that the fornication must stop. Very likely the boy will dump you once he realizes that you won't let him have sex with you anymore. If such happens, it will show his true nature.
Just because you sinned with a boy, it does not mean you must marry him. If you are more interested in the second boy, then let the first boy go and date the second boy. However, you must keep the relationship within the boundaries that God established. No sexual touching (I Corinthians 7:1), no lewdness (Romans 13:13-14), and no sex.
In regards to your past, you don't need to bring it up. If he asks, speak the truth, but keep it general. "I let a boy I trusted talk me into having sex, but I realized that he was just using me and that I was sinning, so I went back to the Lord and dumped him." Don't say who it was with, how many times, or how often. These details are not important. Your current boyfriend is not in competition with your past -- there is a reason why you left the past behind.