When I do running I consistency backache as priod backache but I dont catch length.?

When I go for running I quality period strain but not period.Though my period are irregular since childhood and I am 32 now.I go and get heavy bleeding and cramps and closely of pain during period.But I dont understand ,why I quality pain while I do running?When I stop running the stomach-ache goes sour too.Do I have cysts cancer or something serious? see your doctor love
I own the same symptom when I budge running! I always wondered why that be! I never really worried about it though.