Irregular menstrual cycle. Visa versa?

I always had have irregular period and diagnosed with thyroid. Since 2 years I'm on medication thyrox 75 everyday and dronis 30 to regulate my cycle. When I was on dronis 30 I experienced normal menstrual cycle for 10-11 months. I got married in April this year. I was suggested to continue dronis 30 for 3 months after marriage. After discontinuing dronis 30, I had 2 regular monthly cycles Now been married for 8 months and missed my periods it's been more 60 days so how do I find out if I'm pregnant? And what do you suggest me for regular periods? Should I again start my monthly course of birth control pills for normal cycles? Or it's thyroid playing part in this irregularities? Thus my weight issue is because of thyroid / irregular cycles or visa versa? Hope to receive reply soon. Please find me help. Thank you. Sammabodhi Tojo.