What Causes Hot Flashes When On Levothyroxin?

I take levothyrroxin for several years and tests are normal. Recently I have been feeling very hot and sweaty and after taking off layers of clothing I cool off. Within a few minutes I am cold and my hands are very cold. This continues through the day. What is going on with me? I have an appt. to see my family Dr. Next week. Any ideas?