Unexplained misscarriages.

Ina

Ive had 6 misscarriages. Everytime i get pregnant it only last to 7 1/2 weeks and than no heart beat. My doctor said he has checked everything.... the strange thing is, is that everytime after i have and ultrasound the first time the second time i come back and no hearr beat and still hasnt grown from the first. Any advise? Has anyone had this problem? Please help.