Borderline thyroid issues

Okay need advice! I am borderline thyroid one test lab came back low and my fiancé and I been ttc for almost around 7 months now and last two periods which includes the one now are extremely light and like don't even need a pad. And last period only three days and was done before it usually starts. This time it start s day late but very light like I don't need a pad but I wipe and it's there light. And I pego? Or what's going on this been weird for me? Anyone help tell me what's going on?