I can't stop laughing about everything?!

I can't stop laughing about everything?

When somebody looks at me I always start smiling hugely or laughing. When I was younger and my friends were getting scolded or spanked I always started giggling. I felt bad and I really didn't think it was funny(or maybe I did - but I didn't want to) and I never understood why I always laughed about it.

Whenever I try to voice my concerns or act serious about something I feel is important, nobody takes me seriously because I always burst into laughter when they look at me. My questions are:
How do I keep a serious look on my face? How do I stop finding everything funny?

4 weeks ago
You guys! I even did this before the drugs! I really need help here.

stop smoking those trees