It is possible that you have something going on which isn't right. You need to call the doctor's office and tell them your symptoms. Three biopsies is unusual. Did they say how thick your endometrium is? The test doesn't cause you to get your period. This is not normal.
Mine was 11 and is now 10. The doctor never took more than one biopsy.
Do you have thyroid disease? That can cause the heavy bleeding.
For me it was postmenopausal bleeding due to hypothyroidism.
I hope you get help soon.
It may be that the procedure has brought on an early period. But to be on the safe side I would check your temperature - if it is high than you need to report to the doctor. There is a chance there may be some infection or damage so best to talk with them. But any internal examination plays havoc with your cycle and if your period was due it may have come a week or so early. Ideally you should have been left with contact details and information of what to do if problems like this happened, but it seems you have to make the first move and talk to your doctors. They will ask you about your temperature though, so check that out first. Feel better soon.