heavy bleeding with clots

I have been having a period since April 25, 2017. It has been mostly light with a couple of days of clots and heavy bleeding. I seen OB/GYN 2 weeks ago and pap came back negative for cancer. She wants to do a endo biopsy but Im on a blood thinner and cannot come off to have it done. My issue is today I woke up and was having HUGE clots with bright red blood. I called my oncologist who stated to watch for a couple of hours. I am still having bleeding but with much smaller clots. I am now on day 27 of my period. They have no clue as to why I'm bleeding this way. Ultrasound showed very small fibroid and they do not think that is why Im bleeding. 

Did they check to rule out pregnancy/miscarriage? I have been bleeding since April 22nd. Went in last week and found out I have an ectopic pregnancy and am actively getting treated for it. You need to be careful with things like that. If they haven’t checked to your knowledge, I would take a pregnancy test. That’s how I found out. 

Thank you for responding Olivia. I am 50 and I'm not pregnant. Sorry I should have said my age in my first post. Ive had a ultrasound and pap smear just 2 weeks ago. They are saying its perimenopause bleeding  but Im just not believing it. Im just really scared out of my mind right now. Thanks again for your comment. And I'm glad they figured out what was causing your bleeding.

How old are you? Are you on birth control

I'm 50 and my tubes are tied but Ive not been sexual active in many years so no chance of pregnancy.