Kudos to you for realizing that you want to manage your anger better! A lot of people never figure that out.
Do I understand correctly that you are looking for practical suggestions on how to just get through the heat of "the moment" so that you don't regret anything that happens? Then deal with stuff later on when you have a chance to cool off?
Don't worry about hiding your feelings, that's not good to do that. But, you need to take yourself and your loved ones out of harm's way during that moment. Let boyfriend know the rules, that if you are really really pissed about something that you need your own "time out" and do not want to be disturbed. Physical release is excellent, whether it be going for a run or beating a pillow or doing 50 situps or 100 pushups.
Or write write write into a journal, everything on your mind that is pissing you off, from the crappy day you had at work to the piece of lettuce stuck in boyfriend's teeth to the 5 pounds you gained over the holidays or the coffee you spilled on your new sweater that you wouldn't have if only damnit that goodfornothing boyfriend of yours hadn't made you that extra cup of coffee with extra sprinkles and whipped cream *smile* Anything goes. (Word of caution: you say BF takes this stuff seriously, so do not let him get hold of this writing, since it's just raw feeling and will likely hurt his feelings when the emotions have nothing to do with him. Put it in a safe place or burn it.)
Again, communication is key. Talk to BF about this when you are clear-headed, and make some rules to protect both of you. Remind each other of the rules when these episodes occur, and when the two of you don't handle one quite right, talk it out afterwards and see what went wrong. When you do handle it well, pat yourselves on the back and do something extra nice for eachother.
What do you think of this approach?