Keep in mind Metformin isn't technically for fertility or menstrual regularity.
It's a diabetes drug.The reproductive benefits on PCOS come from the Metformin treating the IR.

On it's own, I find Metformin not that helpful, but combined with a low carb diet I think it is.

Since you have PCOS with IR (I do too), I'd recommend focusing on treating the IR because it will most likely improve your PCOS symptoms too.
I'm assuming you aren't currently trying to get pregnant?

I can't really give advice that because I was diagnosed with PCOS at 14, and I'm still not ready to have kids so I haven't been down that route.