I'm helping my friend solve her menstrual dilemma. She commonly has average pains and normal bleeding which can occassionally be very heavy. However, the problem she faces and wishes an answer to is this:

She ended her period a week ago and has been getting along fine (her definition although I do not call being neausious every evening after taking her BC pill fine) but is constantly feeling sick to her stomach. But today, a week after she's ended, she is having massive cramping (worse than when she gave birth twice) and had TWO blood clots larger than a half dollar come out (which I realize is normal for some women but not for her at ALL) and she has soaked through a tampon in twenty minutes and is bleeding very heavily. She wonders if it could be a miscarriage or what it could be?

Any information is welcome.

Necessary information:
Does have sex regularly but never had this problem before nor does she bleed because of sex.
Has been getting physically sick (throwing up) but has had regular periods for three months.
Takes Birth control.
Does NOT commonly have blood clots (if she does very small and minimal).

Any help for her?