Sun burns symptoms and conditions

I have been on Synthroid since 1983--varying dosages. Side effects have included: weight gain, heart palpitations,adrenalin misfires, extreme reaction to heat (sun burns) and body feels hot all the time, fingers go numb in cold weather. Just recently have not been able to regulate dosage--fluctuating between hyper/hypo. I would like to try a new medication with few side effects. Anyone had any luck finding a different med that works?