TCC is tough, especially after a miscarriage.

You didn't mention exactly how dark the opk was but remember that an OPK is only positive if the test line is as dark as or darker than the control line. Almost a dark as is not usually a positive.

The stretchy cm you mentioned is indeed ewcm- the best kind! You don't have to see it all day though, you can have for instance ewcm in the morning, creamy or wet later on, then more ewcm or even just the one spot of it. It doesn't matter, when you see it it mend you at highly fertile.

And generally speaking the last day you get ewcm is the day you ovulate. So once it's gone you know you've probably ovulated. Although if you note your cm patterns you will probably notice a regulator pattern over each month. For me I get the usual dry and then creamy over my non fertile week or so after AF then it gets decidedly watery then I get about 3-5 days of ewcm including usually a heap on the last day, then after I've ovulated it's notably dry (no cm) although I do sometimes get an extra tiny bit of ewcm a few days after ovulating.

And yes, polycyclic ovaries can interfere with OPKs as people with polycyclic ovaries tend to have elevated lutenising hormone levels all the time, not just at ovulation. They also mean you may not ovulate every month and that ewcm may be sporadic throughout the month, making it hard to track ovulation. And you can have polycyclic ovaries but not the syndrome - pcos - meaning you do t experience the drawbacks and symptoms of pcos.

But then again you might just have longer cycles and not everyone gets clear opk readings anyway. It's not an exact method.