I don't know much about hypothyroidism, however, I would imagine having a gland removed is going to screw up your period. It does involve hormones, and your body has to re-adjust. I know it's hard, but I wouldn't even think about it right now. I would imagine that there's a chance you could skip a period.
I realize you're excited about becoming pregnant again, so I know it's hard to just not think about it. I just know that when I just relaxed about it, I felt much better, and that's when I did get pregnant.