I only bleed for one day every six weeks

I don’t know why. Im only 25. I’m not on birth control. My hormones are normal (well, they never tested estrogen or progesterone but my testosterone and thyroid are normal).

I had an ultrasound my endo thickness was 3mm which supposedly is normal but why am I not really getting a period anymore. They even refused to test my estrogen bc they said it “fluctuates. “

But if I’m only bleeding every six weeks I probably can’t get pregnant right?