We broke up and I owe him an explanation. What should I say?

Me and my boyfriend broke up some time ago. I love him more than life but I can't be with him anymore. We dated for a year and a half and our relationship was great before we had sex. I was a virgin before and I always wanted my first time to be with someone I truly loved. We waited 1 year before we had sex. That night he cooked dinner, lit candles, the whole nine but it was nothing like I expected. I thought maybe that was first time jitters, but same results the 2nd, 3rd, 4th, etc. I hated having sex with him. I dreaded it completely, but I was afraid if I kept saying no, he would break up with me so just tried to get through it each time. The sex felt really really good, but afterwards I felt horrible. The next day I would be really irritable and depressed one minute and anxious and angry the next. I couldn't tell anyone what was wrong with me because I thought they'd think I was acting like a baby. I kept telling myself, in time I'll stop feeling like this but I didn't. It took about 6 months for me to figure out that I wasn't ready to have sex and I hate myself for that. I mean, I'm 19 I live on my own, I had an amazing guy but touching him makes my skin crawl? How f***ing lame is that? So a month ago, I told him I want to break up. He kept asking why and I said because I want to be single (I had to tell him something) and he said forget you and that was that. 2 days ago he texted me and said that couldn't have been the real reason we broke up and that I should tell him the truth and I know I should but I can't. I love him, but I obviously have personal issues I need to work out before I get into another relationship, but what should I tell him?