Boyfriend problems.... Help!!

I've been with my boyfriend for awhile and things were pretty good but recently things just started going downhill. I've been told by some people that he's known for lying and he's tried to hide things from me. I broke up with him for like 24 hours and the next day I said "You have one more chance. Don't screw this up." That warning wasn't clear enough. I found some stuff on his phone that he let his friend show him but "it wasn't what he thought it was". Whenever I just don't want to be near him he follows me after I say leave me alone. My friends don't even like him. The problem is: whenever he leaves me alone, I miss him and I'm afraid he'll do something to himself if I leave. He relies on me so much emotionally when I can barely support my own emotions because of things going on at home. He's not a sensitive guy either. He always tells me to "suck it up" or "stop being grumpy" or "just ignore it". I don't know what to do anymore. Help!