What Causes Unusually Heavy Periods With Cramping And Stomach Discomfort?

Hey, I just started my period yesterday it is super heavy with alot of clots and alot of cramps. Me and my boyfriend have been trying to have a baby for about 10 months now. My period was a week late i took ten home pregnancy test one was positive 9 were negative. I went to the doc and was tested they only checked my pee which also came back negative. When i finally got my period the cramps were so bad that i couldnt eat or even get out of bed i had to take alot of aleve for the pain. My periods are never this heavy and cramps have never been this bad. also before i got my period i was eating alot was very tired have cravings and had horrible mood swings and pulling in my stomach. What could this be?