Keppra Rage

I am desperately seeking advice. I am engaged and my fiance has epilepsy. We have been together 5 years, and in the past couple of years since he started taking keppra, he has drastically changed. Most of the time, he is his normal self, the person I love, but he often gets extremely irritated and freaks out, yelling and cursing, not just at me, but at other people as well. He seems to have no ability to cope with the slightest issues that would roll of most people's back without so much as a second thought. Even worse is that every so often (once a month or so) he flies into these uncontrollable rages that absolutely terrify me. We will be having a normal conversation, both in great moods, and suddenly he is kicking walls and throwing things with a blank stare like he isn't even really there. It really scares me and this never happened before the keppra. He isn't honest with his doctor about the side effects because he is too afraid to get off keppra and try something else because he thinks it will trigger seizures during the transition. Does anybody else have experience with this? If so, has anything worked? I got him to try adding B6 vitamins but it made no change. I want to get him help because I know it isn't really "him" when he goes into these fits, but I am at my wits end...Please help!