I have this 'nervous laugh' when I talk, not always but a great deal of the time. I do it so much it's more like a tic than anything else. I can't help it.

My uncle, however, who I do not know to be diagnosed with anything, also does it. And he also has that "randomly starts laughing" thing. Me and my cousins used to discuss it because he would do it a lot. Say at Thanks Giving dinner the table will fall silent and then suddenly there's my uncle laughing into his plate. So I wonder if it's more an anxiety thing rather than a bipolar thing?

Also, the over reacting or reacting incorrectly, I also have that problem. You should keep a mood chart and track that type of thing to show to your doc.