Misscariage or ??

I am looking for any input on my situation... Dr's seem to be unsure what is wrong with me an I am worried my time is running out. Here's my situation...
I had been spotting but never got my period and on Aug 10 my first HPT was positive. I had an ultrasound on Aug 14th which showed 5-6 cm fibroids in my uterus (lot's of shadows) and no gestational sac was found... still spotting... On the 14th my HCG was 1680 and on the 17th it has gone up to over 3000. still spotting until Aug 21st when I started bleeding moderatley. on Aug 24th my HCG was over 8000 but that evening I passed two large clots (golf ball size) I continued to pass large clots and bleed moderate to heavy (NO CRAMPING) I went for another ultrasound on Aug 28th and they foung a gestational sac appox 5 weeks (no yolk or heartbeat) it was expected I was 7 weeks. I was sure I was haveing a miscarriage but went for another HCG which came back over 9000. I am still bleeding and still passing clots but no pain at all (except sore breasts)

Today dr sent me for another HCG, blood group & anitbody, coags, fbc, uec and lfts.

My history... I has a DVT resulting in a PE in 2001 (diagnosed that it resulted from birth control pill)

If anyone has any insight as what is going on I would appreciate your comments... I was greiving a misscarriage and now I don't know what's happening...