Would love your input!!!

So, I stopped taking birth control about 4 months ago. My periods have been normal and now, I haven't gotten my period in like 40 plus days. So, I took a few pregnancy tests and, nothing!! I've gained about 20 or 30 pounds in the last like 6 months, including 5 in this past week. Actually have been more active and eating a little less than i normally do.very sleepy as well. Do you think this could be my thyroid??? Any thoughts/ inputs would be great. And yes I have an appt for doctors this week. Just want input!