First Time using Letrozole: need advice.

I have PCOS taking metformin and prenatal vitamins.

Dr had put me on birth control to regulate my periods which it happen had 5 to 7 days periods on September, October and November. In November Dr Prescribed me Letrozole (first time session) to start my ovulation going on cycle 3 to 7 day. Everything was good took the clear blue ovulation testing with the smiling face and had sex with my partner. I felt like I did everything correctly but when December 6 and Dec 7 came around I had blood(red) spotted on Dec 6 and Dec 7 red brownish more brown tho. I told myself it didn’t work. And it was too soon for my period. I took a pregnancy test it was negative and now I have not started my period am days late . Now I don’t know what to do. I messaged my dr about the problem and he gave me two options to start again for my second around on birth control for four months with taking letrozole on the fourth month or get a referral to a reproductive specialist to do IVF.

Has this ever happened to anyone else? Taking letrozole and then all of sudden no periods and everything is negative. I feel very sad.