I've been on Synthroid since November 2007. I've had several side...

I've been on Synthroid since November 2007. I've had several side effects that's been driving me crazy. From night sweats, trouble breathing, can't stand heat, mood swings, stomach pain, insomnia, and menstrual changes. The side effect that's having me worried is my menstrual cycle. I started my cycle Jan 5th and during this time, my doctor switch dosage. He started me out with 100 and now I'm on 50. I'm very petite and I knew 100 was too much for me when I weigh 110. I've been spotting since and today is Jan 19th. I told him about this and I asked him if the medicine caused this and he said no to contact my GYN. I never had this problem before and I've been so stressed about it. I told my nurse at home about and I did tell her that the thyroid specialist said it wasn't a side effect of Synthroid. Also, I told her that I did research and it did mention menstrual changes. So I have to meet with her next week. Am I the only one having this problem. I want to have children in the future and I'm worried.