perimenopause symptoms

I am on T3 only and feel better than I have done in many years. I am 52 years old. Just recently I have missed 3 periods. around about the time my period should happen I get really bad missed heartbeats. They last on and off for about half an hour, an usually only happen once in the evening when I am resting. I am more tired and feel quite anxious. I went to my GP and he just said that maybe I should cut my T3 down. I said I wasn't going to do that as I felt much better since I increased it to 60mg nearly a year ago. I asked if it could be anything to do with perimenapause and he said he didn't think so as I wasn't getting hot flushes or nightsweats. He told me to go back in a week if I wasn't any better. I don't want to go back if I am not better because I don't want to risk him cutting my T3 down. Any ideas please.