Serious menstrual cramps?

I am 27 now and since I was about 20 I have had very severe cramps. It usually only lasts 2 days but for those 2 days I am not able to function. I have to take an overdose of Ibuprofen and lay the whole day in bed with a heating pad. I've tried many different pain killers including a few prescription narcotics but nothing helps much. My other symptoms include (but not always) Diarrhea, vomiting, blackouts, cold sweats accompanied by hot flashes, and pain throughout my entire body especially my abdomen, thighs, and lower back. I have been to several Docs who have all done paps, blood tests, & sonograms to check for any cysts or endometriosis (not sure of the spelling on that one). They've found nothing. Recently I have noticed that I will start spotting about a week or so before my period and even occasionally when I am ovulating. Does anyone have an ideas? Could there be something wrong with me that the docs are missing? Could there be some hormonal thing going on?Or is it that I am just a very unfortunate woman who gets bad cramps? Oh, I don't know if this has any relevance but my mom started going through menopause in her early 40's. Could there be some genetic correlation?