Hello flyingplum, didn't want to read and run.
I'm sorry for your MC and that you're in that tumultuous, worrisome place at the moment. Hang in there!
I have PCOS too, had 3 losses in 2018 (between 5-12 weeks) followed, finally, by a successful pregnancy in October 2018, which is now at 20 weeks.
First thing's first - pregnancy tests at this early stage can vary and can throw up slightly different results depending on brand (and therefore sensitivity), how hydrated you are and whether you're testing with FMU or not. Even if you're certain that everything is identical between tests, and that you're testing correctly (i.e. on looking after the designated time only, not much later than guidelines) - the manufacturers still say that the faintness of the line doesn't count for anything. It's the line itself that matters. hCG levels do vary massively between women, if you have a look at hCG charts by week online, the ranges are quite big. All of that probably isn't much consolation, but do keep it in mind.
With PCOS there is, unfortunately, from what I've read, an increased risk of MC. I have never been able to get to the bottom of exactly why that is though, apart from vague theories about hormone imbalance and inflammation. GP not much help either. This pregnancy, I have been taking 'baby aspirin' daily, and still am. It seems to have worked, even though studies show mixed results and inconclusive proof. If you read up on it, you can talk to your GP/MW about it.
In my case, I was so desperate I started taking it straight away on finding out and then told the GP after about 2 weeks. She wasn't keen on it, because it can cause excessive bleeding in the mother, and stuff like stomach ulcers, but I carried on anyway because she agreed I had no known pre-existing conditions that would make this particularly dangerous and that it can be administered in pregnancy. At 14 weeks the obsthetric consultant said it's fine to keep taking, mixed results but can't hurt and agreed it might have helped. So I still am. I'll never quite know whether this is what helped or whether, finally, my body just got into gear and finally produced a viable embryo. But it's worth thinking about.
Hope it all turns out well for you and do come back on here as you go trough this, there always someone around.