Period is 3 days late...

Hi All

I have pcos and I've been trying for 8 yrs now. I had my hsg done on the 29th of September, results were great. Both my tubes are clear. My uterus is perfect. My doc put me on 500mg metformin,folic forte acid and inofolic. My period is 3 days late. I have tested with a bfn on 12dpo. Did anyone experience late period while on metformin or inofolic? My doc is giving me 3 months on this medication. If I'm not pregnant by December, my doc is starting me on femara together with these meds. I have been on femara last year and got pregnant but had a miscarriage at 8 weeks. Any advice will help. Thank you.