Suggest Treatment For Dizziness And Nausea While On Thyroxine

I was diaognised for thyroid papillary carcinoma in aug 2012 and was operated for total thyroidectemy and subsequently done I131 therapy and on 200 mcg thyroxine. I am feeling dizzy most of the time, feel nauseated and lately feeling mentally sluggish. Also my weight has increased quite considerably. Have to visit tata hospital every year n reports are normal. I also check in between 3 months privately. I have anxiety too. What should i do ??? Coz its intefering with my daily work in oman. Kindly advise