What Causes Heavy Menstrual Periods?

i have been having many issues with my menstrual cycles and my dietary functions. i have a few large fluid filled cysts next to my lower spine. these cysts grow with my cycle and with my back pain. i was just diagnosed with ibs but i have only recently been having the ibs symptoms.(2-3mo). I am wondering if the cyst possibly blocks my dietary track when it grows so large(softball size). I have pointed these cysts out to 4 different drs and they dont seem to respond .I also am wondering if this is why my periods have been putting me in the hospital