Could he be cheating or am I just being paranoid?

We just had a huge fight 4 days ago. It was because he keeps doing really mean stupid things like taking my bus money out of my wallet (only a few dollars but that makes me late to work!) and being gone half the day at his damn friends house then coming home being lovey for an hour and expecting sex, and more...anyway 4 days ago I decided I was done with it. He just got defensive like always, stated he was not going to change anything, and I said because of that I was breaking up with him. 6 hours after he left again, I broke the f*ck down, bigtime. I tried to be strong and convince myself it was for the better but in the end decided it wasn't worth it, I'd rather try to deal with that level of problem than be without him, he's overall still the best thing that ever happened to me. I called him and he gave me a long list of everything that I do wrong, all of which is true: I have some gnarly mental issues that cause depression and severe anger problems (ask me if I can get help, the answer in this economy is a resounding NO!). Anyway I *begged* him to come back. Shamelessly. My pride could go to hell, and it did.

He reluctantly agreed, we both said we can change things, but mostly me with my freakouts, and we've actually gotten along better than ever...but the last 2 days he's been gone all day. I literally saw him for 5 minutes today, maybe 30 yesterday.

He has good excuses most of the time that make sense, except maybe when he says he fell asleep in a house full of people and nobody woke him up, or he got sick and couldn't come back for a couple hours (he does have a stomach disease but usually he comes home till he feels better..) I don't know. He's threatened to "find someone else" before but only when he's super angry. He *always* gets defensive when I ask him about anything (mostly because he doesn't feel good) but that makes it impossible to judge his reactions... would a guy get back together under an agreement of change and then go cheat cause he really didn't want to??? I have no idea.. please help!