When you're in stitches, you are laughing uncontrollably and could use a few synonyms to describe your situation. If your side-splitting laughter is unstoppable, you can say you're in hysterics. You could also be in fits, which is an excellent way to describe when laughter comes in bursts. Guffawing is another alternative to be in stitches. Unable to control your laughter, chortling fits this bill as well. A few other words that could fit the bill are howling, roaring, or convulsing with laughter. If your sides hurt from so much laughter, you could say you're doubled up or bent over with laughter.