No advice for you sorry, sounds like you've had a really hard time of it though.
I was thinking given your recent surgery you could ask for referral onto a Gynae? Or Fertility clinic, they might be able explain why your cycles are all over the place.
Are you referring to AF only sticking around for 2-3 days? Mine are normally only 2 days, sometimes rarely 3-4.
Regarding the HcG levels, that is quite low, I had a very early MC as well, in fact I had what they call a Blighted Ovum, so there was never even a fetus that started to develop, I knew at 5 weeks (from the inactivity on the dating scan), but it wasn't confirmed until 8 weeks and my HcG was 850. Not that I'm saying that I'm "normal" and you're abnormal, just that was my experience, did they say if they had any cause for concern for such a low level?
Take care, hope it all settles down for you soon