Relationship problems

Me and my boyfriend have been dating on and off for the past two years and now I'm finding no matter what we do sex is always boring for me now. It's getting so bad that I'm faking orgasms and he only last for a few minutes never any longer it's not enough for me. Not only that we're having other problems too and I just don't know if I feel like he's it for me. What do I tell him? I don't necessarily want it to end because we do have good times but I don't want to waste my time.