I can kind of understand where you're coming from. I was with my boyfriend about 6 months ago, and when i had a great loss, i couldn't cope with much, and basically i went a bit up the wall with grief.. and i didn't think it was fair on my boyfriend as he was also dealing with a loss, only not quite as great as mine.
We didn't talk much really because we were both hurting, however in March he was on a night out and was in the nightclub i work in, and just blurted out drunkenly that he was still crazy about, i laughed it off and said "you're just drunk".. but from that.. we started to get close again.
End of March we both went on the same college trip to Spain, and we'd agreed to try and sort things out while we were over there. While we were over there.. i found out he was texting a girl who he knew back home.. none of this bothered me, as he told me she was purely a friend. We never sorted anything out.. just argued a lot. One night i got a bit homesick, and got a bit upset. So he went to go and talk to my best friend. I'd had his phone listening to his music.. and he'd assumed i'd been reading his text messages which was why i'd got upset. So then when my best friend told me he'd said this.. my first thought was "well why? what's he got in his messages that he shouldn't have that might possibly upset me" I say shouldn't have, because she has a boyfriend.
When we got back to England.. i heard many a rumour that the day after we'd got back he'd met up with said texty girl.. one thing led to another and in the end it all esculated and he was taking pictures of her.. and the day after that.. he'd slept with her. I was livid. One, for the sheer fact that i, his ex, was still on the scene, and two, we were supposed to be sorting things out and seeing where we could go.
I eventually confronted him, and he denied it. The conversation ended in tears for the both of us, and we thought the best thing was to cut each other out of each others lives. I hated this other girl.. basically because she had what i wanted, my boy, and she had her own boyfriend, why did she need the one thing i wanted?
Ironically, instead of seeing less of each other, we started to see more of each other at college etc, he was always out at my nightclub at the weekends, and the cutting out thing fell through.
We ended up getting back together a month ago yesterday and at first i still had my doubts, so i sat him down and we spoke about it. He promised me he hadn't and he'd only ever wanted to be with me, and she was purely just a friend. Whether he was telling me the truth or not i don't know (some people commented on how he may have been lying to me) but i believed him.
You just need to build up the trust, that's the only way you can get around that one.. but definately definately you need to sit down with him and have a good conversation on how things are going, why he may have trust issue, tell him you don't think you can fully trust him. And as for his anger.. tell him you're scared he'll lash out again. All you can do is talk, or nothing is ever going to get sorted, and you can't live your life scared of what he might do next.