How do I end this relationship and stay friends?

I've only been dating my boyfriend for a little over 3 months and things got serious between us pretty quickly.. he seemed so perfect for me, like everything I'd ever envisioned. He's 25 and I just turned 21, and while I thought when we first got together that I was ready for something serious I am slowly starting to have doubts. Now to make things worse I feel as if I am losing all ual attraction to him!! Everything else in our relationship is SO PERFECT but the thing is making me crazy! I don't want to do it at all anymore and when I say no- he gets upset with me!! We have already gotten so close in the past few months, I feel as if we might as well have been dating years! I don't feel as if I am ready for something so serious and I have explained this to him many times but his response is simply that he doesn't expect me to feel as ready as him... I've tried to tell him that I have lost my ual attraction to him but I just know how much those words are going to break his heart. I've tried to tell him that I love him but I just am not ready for something so serious and I don't feel as if I am in love with him anymore... He says he doesn't understand how I can not be in love anymore and if we break up he doesn't want to try and be friends and yet he also says that he thinks we will get back together anyway... I don't know what to tell this sweet boy who has given me his heart without completely destroying all of his trust in love ( he has a lot of trust issues from cheating gfs of the past) PLEASE! Help me figure out how to get through to him about how I feel without completely crushing him!!!!