Metformin

I am just wondering if there is anyone else ttc who is on metformin for pcos and has had a crazy cycle change. I went from a 29 to 31 day cycle to 40 day according to glow. I would normally have gotten af on the 1st of January but so far nothing and i have taken five tests and they have all been negative. I have been on 1500 for almost two months now and ttc for 8 months.