Missed period last month, very light period this month lasting 2 days. no chance of being pregnant. could it be a thyroid issue?

Possibly: Hi. One of many possible effects of untreated hyperthyroidism is lighter periods. Usually there are also a number of other signs and symptoms in hyperthyroid people that you don't mention. Do you have thyroid disease? If so, is it treated? Please feel free to provide more information. When was the ovarian cyst removed? The transfusion? There are a number of conditions that can throw off periods.