I wouldn't worry, it just means your crazy. By which I mean human. We're not always in control. I've lost it like that laughing with no permanent harm, just a bit oxygen starved and sore around the middle (Then again I'm probably not a very reassuring example...). And it probably does come from some place darker and scarier than normal laughter, but for whatever reason it needed to come out. Least you weren't at a funeral or something, the kind of places where that usually hits me.

There's a one-panel newspaper comic I saw years ago by a fellow named Joe Martin that I'll never forget. Mr. Boffo, his clothes in tatters, is standing with his dog on a desert island just big enough to hold them and one sorry looking palm tree. He muses: "Someday, Weederman, we'll look back on all this and laugh. True, it'll probably be one of those deep, eerie ones that slowly builds to a blood-curdling maniacal scream, but still it will be a laugh..."

Hmmmmmm, that might make a good signature quote.
~~hugs, Veronica