Anyone else here have an indigestion-like feeling on their period?

The first day of my period (usually the heaviest flow) I get this uncomfortable feeling in my intestinal area like when you eat something funky and your digestive system doesn't like it. Feels similar to indigestion. I've had this for years and it really hasn't changed. To clarify these are not menstrual cramps, I have those as well and this is not the same thing at all. It only ever comes on my period and gets better as my flow gets lighter. It's not "painful" it's just an uncomfortable feeling. Before I went on BC it felt so bad sometimes I had to stay home from school. Do any of you have this? I haven't found anyone who does yet and haven't found anything online about it.