Has anyone ever felt period like cramps 10 minutes in to jogging that gets worse when you stop. It goes within about 5 minutes and I feel fine then. I've noticed this since I first started my period at 11. I'm 20 now. Sometimes it's worse than others, only seems to happen with running though and that is usually only around a sports hall a couple of times, but it really puts me off running. Doesn't seem to happen if I've done other exercises first though. Any ideas?