It could be a hypomanic state. I know I get really irritable when I'm hypomanic, to the point of being angry all the time. It's like I can stay angry for days with very little provocation. There are other indicators such as sleeping less, and more energy. Much like a manic phase but not as severe. I used to internalize all my anger, too and now it seems to seep out.

I'm not sure how you could get your team to pay more attention to the problem, but I think it is important that they do. I do think it is probably the bipolar. Of course, I'm not a doctor.