TTC for 2 yearz and my period lasting almost 3 weeks...TMI?

I have been havin' very light spotting for the last three weeks or so...with mild to sevear lower tummy pains with diarrhea...what would cause this? I was about 2 months late on my monthly, and has been since i had a miscarriage (that'z what the doctors seem to think anywayz). For the last about week in a half i have been havin' the runs and just not feelin' myself. My stomach is super tight almost all the time even when i don't eat...i thought perhaps it was just a stomach bug but startin' to wonder if it isn't more. I am 26 yearz old and other then my monthly bein' wonky im in good health.