How to let go of someone

I've been with my boyfriend for a year and 2 months everything been so good but I just feel like he isn't fully commited to me (not like he's cheating or anything he just doesn't care about our relationship anymore like he use to.) I'm struggling on how to break up with him cause he's my only friend and i love him a lot but I'm so miserable in our relationship. People think we're the happiest couple ever and we use to be but I just feel like this isnt what we both want anymore. Please help me I dont know how to say and how to get through a long term breakup. He's everything to me, we've been through so much, I feel like since he's going to college he doesn't want me anyone I'm holding him back from enjoying himself. Do you think it will be wrong if I just stop all communication with him? I feel like that's the best way for me to end things, I know he don't beg me to come back and I have to leave him. We've talked about our problems already in case anyone says does he know what you feel yes yes he knows he says we'll change it but after a day it goes back to the same thing.