I'm like that all the time.
I can't tell a joke without laughing before, or during the punchline. I laugh at the slightest thing, as if they were the most hilarious thing in the world. Most friends think that I've been smoking pot because I'm constantly giggling at nothing. Sometimes I'll just remember something hilarious in the middle of a serious conversation, or during a meal, or anywhere, and I'll just start laughing hysterically even though no one there said anything funny. Someone will say something unintentionally funny, and I'll laugh so much, but can never tell them what it is they said that was funny because I'm too busy laughing. There's an 80% chance that I laugh until my stomach hurts whenever I laugh, and yet I can't stop, and it's so painful. I regularly spit out my drink during meals because I find something funny, and I can't watch TV and eat for the same reason. If laughter really is the best medicine, I should be the healthiest man in the world.