I that way too sometimes. It's mostly when I feel really ashamed or bad about something. Only 1 therapist mentioned anything about it before I could blurry out it's a coming mechanism that I use when really ashamed or anxious about something. It makes me more ashamed when I laugh at times like that. Tho part of me is really laughing... that's the worst part. But mostly it's just a nervous reaction, like u was caught with my hand in the cookie jar... I think it has a lot to do with getting through past abuses as mentioned above. I know I was never allowed to cry, but I would laugh to get my dad to start laughing so he wouldn't be quite as mad at me.