Delayed periods. Tablets regularly?

Hi. I have pcos and was in treatment.. I'm taking metformin tablets and folic acid regularly.. My LH value has been reduced to below 6 i.e 3.67 and for the past 3 mnths my periods was regular.. My Lmp was on July 24th.. My doc suggested me to plan for babe  and I was in follicular study up to 18 days after my periods.. As the follicles were not developed properly she said let's try it in the next cycle with more dose and injections.. But I dint get my periods last mnth.. So I consulted my doc once again on my 42nd day.. She scanned and said I'm unable to locate anything so go for a hcg test.. The result is below 1.2mi and negative.. She still asked me to wait for one more week and take a urine test.. Today is my 50th day and I took the urine rest.. I got one dark line and one very dull fainted line.. Do I want to wait some more days and take the test again.. If I'm not pregnant, wats the cause of delay in periods even when I'm taking the metformin tablets regularly? Pls reply