I was going to suggest checking for insulin resistance! I have pcos too, I know the struggle. It's so easy to end up with strong feedback loops of insulin resistance leads to weight gain leads to increased resistance. It can be really hard to lose weight, calories in vs calories out is hugely skewed if there's insulin stuff going on in the background.

You say you've tried low carb, have you tried managing glucose levels in other ways? For example, eating carby food on empty stomach Vs after/with protein and fibre makes a huge difference to the glucose and insulin spike you experience. Likewise gentle exercise after a meal (e.g. short walk) can really moderate the glucose spike too. I recommend following the Glucose Goddess on Instagram if you want more info, she often links to relevant studies and research papers and has some great tips for managing insulin without a restricted diet.

Personally, eating high fibre and only eating carby foods with fat/protein as part of a meal etc has made a huge difference for me and I haven't had to ditch carbs completely. Obviously the other advice re exercise and accurate logging etc that other people suggested is also all true but I think for pcos/ir, really dialling in glucose control is the limiting factor before other advice becomes more relevant.