I also often feel really bad after an arguement. I feel I've gone over the top and responded unnecessarily aggressive, or made bigger of something than necessary. I feel guilty about it, and end up sending an sms or e-mail to my boyfriend to apologise.
I don't know if it's a case of discerning between the bipolar and rational you. I think that when you aren't stable, the consequence of being bipolar is that you cannot control your actions and thoughts and thinking in a rational way.
Not sure if the difference I'm trying to make is obvious and clear?
But to cut a complicated story short - I don't think you're alone in this. I think therapy can help teach you coping mechanisms, and if you can learn ot give youself some extra tiem before responding in order to rationalise your thoughts, it will also go a long way to a happier you.

btw - sounds like you have an awesome man there!