Need advise

So I've been on Letrozole and Metformin.. I did my 4th cycle last month.. on sept.. I got an ultrasound done because apperantly my follicles are not big enough, which means they don't mature. On my 3rd cycle I had good news I had 2 follicles good size..I was so happy.. but then I got my period so no pregnancy.. so I started the 4th cycle and when I went to get the ultrasound done got bad news.. my follicles were not big enough..broke my heart.i felt like I was back at step one. So I've never had my periods regular but since I've been taking letrozole I've been having my period every month without no medication.for the last 2 months I had it exactly on the 18th..and for the other months the latest ihad it was by the 18th..so this month has been the longest that I haven't had my period since started taking letrozole.. so I was expecting it on the 18th,19th..and today and nothing yet.. I need advice. Should I wait or should I take a pregnancy test? But if he said my follicles were not big enough at that time, I can't be pregnant? I don't want to get my hopes up.. HELP