And not like "I-just-ate-and-then-ran" kind of cramps. And I've been a runner for years. But it's literally exactly like menstrual cramps. Has this happened to anyone else? Why does this happen? And how can I make it go away?

i have been a runner since i was very young. i get them every once and a while, and when i get them it usually means that my period is  late and it comes within the next week or two. the only way i have found to get rid of it is midol.

Is there any chance you could be pregnant? If there is not any chance you are, than try something for gas. Either way you might want to talk to your doc.

Have you seen your doctor about it?