I have something that's been bothering me lately, and I have to get it out somewhere.
I started dating this girl four years ago for two years. While we were dating we were completely in love and agreed that we wouldn't have sex until marriage. After we broke up my loneliness pressured me into a relationship which led to sex one time. I remember afterward how terrible I felt because I knew my ex would have been so disappointed in me, and I still had feelings for her. Her ever finding out haunted me for the next year, in which we didn't speak. At the end of that we began talking again.
She turned me down for another serious relationship which sent me spiraling down into another sinful relationship, which led to several sexual experiences.
A few weeks later she came back and said she did want a serious relationship. We had already caught up on the year we missed out on but spoke more of our past exes. When she asked if I was still a virgin, I couldn't tell her. I just couldn't. I lied and said "yes." More than once shes asked, and I've told her I was because I knew if she knew the truth, it would be over.
I love this girl more than anything, and it would break her heart, too, I know. We loved each other the whole time and still do very much. I've repented and God has forgiven me. But it feels so wrong taking her down a long and serious path when I know she would've never gotten on this path had she known. The guilt comes and goes. When I'm with her nothing else in the world matters. We are so happy. And I forget most of the time. But sometimes when I sit here and think of when or if we were ever married, she would think that we were pure together, but that's not the truth. Sometimes it bothers me but others it doesn't. I just don't know what to do.
"Blessed is the man to whom the LORD does not impute iniquity, and in whose spirit there is no deceit. When I kept silent, my bones grew old through my groaning all the day long. For day and night Your hand was heavy upon me; my vitality was turned into the drought of summer.
"I acknowledged my sin to You, and my iniquity I have not hidden. I said, "I will confess my transgressions to the LORD," and You forgave the iniquity of my sin" (Psalms 32:2-5).
I believe you do know what you should do, but you value this girl's misplaced respect more than the Lord.
Lying is never acceptable because God is a God of Truth. "But the cowardly, unbelieving, abominable, murderers, sexually immoral, sorcerers, idolaters, and all liars shall have their part in the lake which burns with fire and brimstone, which is the second death" (Revelation 21:8). While I don't suggest bringing up the topic of past sexual sins, but if asked the truth is owed. If past sins may lead to future problems, such as an STD or a child that needs to be supported, then it needs to be discussed in advance of marriage. But at the same time details should not be given. The other person doesn't need to know who you had sex with, how often or in what way.
The fact that she asked you repeatedly tells me that she at least suspected that you lied. But I also wonder if she was looking for an opening to discuss what happened to her in the time you were separated. While you are certain that her knowing that you are no longer a virgin would end the relationship, this isn't what she told you, it is what you assume to be true. You might be right, but you just as likely could be wrong.
Think of this, too. If you two do marry and she finds out that you lied about your sins, what is she going to conclude? How will she ever feel confident that you aren't out committing adultery and lying about that? How will you ever feel that you truly have her love if you always see that what you have is founded on a lie?
You started out on the wrong foot. You need to straighten it out, even if it means she leaves you again for a while.
I'm glad to hear that you've repented of your sins, though I find the way you excused your sins to be disturbing. It almost sounds as if you had sex as a way of getting back at her. You said it was loneliness, but that doesn't quite match what you did. You were dating someone else, so the loneliness should not have been there. I'm bringing this up because I don't want you to fall back into sin and it is important to know where your weak points are so you can guard against them.