Letrozole when I ovulate with metformin already

Anyone in a similar situation? I have PCOS. I had irregular periods so I was put on Metformin which seemed to regulate my periods down to about a 30 day cycle. But that’s been 4 months now and nothing. So this cycle we are doing Letrozole. I’m not sure what the Letrozole is supposed to do for me if I already ovulate...I’m worried it’s going to over stimulate? My OBGYN doesn’t seem too concerned about monitoring me...any thoughts or feedback would be much appreciated!