One of the side effects of birth control pills is a temporary lack of ovulation after coming off the pills. Cycles without ovulation are usually irregular. Ovulation is usually re-established in 6 months. The maximum waiting period is 2 years. The symptoms you’ve mentioned (sore breats, nausea, lack of appetite) are not signs of thyroid disorder. There could, however, be abnormal levels of thyroid hormones without typical signs of thyroid disorder. Thyroid disorder could be the reason (or one of the reasons) for sterility. You can request hormonal analyses: FSH, LH, estrogen, progesterone, prolactin, and thyroxin. It is very important to find out if you are ovulating, or not.