Explicit details ahead

Let me get this straight, you can never truly know if he's cheating unless you find out for yourself. Until then, you can only assume, or strongly suspect.

I didn't suspect anything when it happened, and so far I only know about one time. It was the night after prom night, (I'm older but my best friend didn't have a date so she invited me to go with her). I was working a 2pm-8pm shift and it happened between that time.

I remember when I tried to have sex with him that night, he got soft really fast during the act. And I thought it had something to do with me, I thought I didn't do enough to please him. I got upset.

But other than that, it was like nothing happened, he acted normal and like nothing went on.

It wasn't until 2 weeks later that I found out through the girl he did it with (my so called best friend) that it happened.

I felt really betrayed, really hurt, and my trust was wiped away.

He begged me to stay with him, that he made a mistake; but I didn't know what to do. He was crying and driving me around everywhere we used to meet up when we met, he talked about all of the things he had planned to do with me to further our relationship.

I was dead inside, I felt like he had no right to try to convince me of anything.

My "friend" began telling me he flirted with her and said he would fuck her for weeks, and I believed it. I didn't know anything anymore, I didn't know up from down.

He denied everything she said, saying she was twisting his words. He tried to make everything up to me by buying me flowers, hugging me all of the time, and telling me sorry constantly.

She kept saying he lusted her and wanted her, and he keeps denying it.

I don't know what to think anymore. I hope someone can give me advice here. I can give more details if someone asks.