Hi, I Have Gone Over 2 Months Without A Period.

Hi, I have gone over 2 months without a period. Home pregnancy tests and blood tests have come back negative. Went to see a fertility specialist as my husband and I are trying to conceive. Gynecologist initially diagnosed me with pcos, but the fertility specialist did a transvaginal ultrasound and said everything looked fine. He even spotted a sac, but said it's possibly just a pseudo sac because another round of blood work came back negative. That was 2 weeks ago and still no period. Any idea as to what's going on?