Understanding hCG Levels and Potential Miscarriage Symptoms

Question
So I tested positive on a home pregnancy test on Feb. 2nd and did a follow up testing at a local clinic which was confirmed. They judged that by my last period (which was Dec. 4th) that i was 9 weeks. Then on Monday the 6th of Feb I passed a small blood clot and began to spot. I called my Doctor, went in and did blood testing and a vaginal ultrasound. The ultrasound saw thickened lining of my uterus and that I had ovulated but no sign of a baby at all. I got my hgc level results back for Feb 6th and they were at 500. I started bleeding very heavily on Feb. 7th and called my doctor. They informed me this was probably a miscarraige and that I needed more bloodwork. I did the next round of bloodwork on Thursday Feb 9th. The results of that test was that my hgc levels rose to 900. I'm just having whiplash from not knowing what is happening. I know that after we found out the first time, my fiancee and I have had intercourse on the 2nd, 3rd, 4th, and 5th. So I wouldn't think I got pregnant then after immediatly miscarrying. And I cant figure out whats going on. but I actually took a test on january 12th and it was a very very faint and partial possitive, but I took a second test and it was negative. So in general Im just so confused and I really need some help. If I could at least get some Ideas of what it could be that would be a great help since im just sitting in limbo with no known options.

Answer
Dear English

Levels of hCG are really not diagnostic or reliable to make a diagnosis. Therefore, if the ultrasound excluded the possibility of ectopic pregnancy and showed nothing inside your uterus except thickened lining without any remnants of conception, then you have nothing to worry about.
My advise is to repeat the hCG level after 2 weeks to make sure it is declining. If is still rising, the possibility of what is called "gestational trophoblastic disease" should be considered and investigated.

Good Luck