Good Morning Doctor! I Was Diagnosed With Severe Hypothyroidism Over

Good morning Doctor! I was diagnosed with severe hypothyroidism over 1 year ago as a result of a routine lab exam. My TSH was 100! I received the call from the MD's office early the next morning. My concern is that my body is "morphing" into a beer barrel. When I graduated from college I weighed in at 216lbs. I lost over 110lbs. on my own by walking everywhere & staying on a 1200 to 1400 calorie diet .At present I am taking 100mcg daily, no diet change, thyroid is within range, but I keep gaining weight. Any suggestions?
MY EMAIL IS OUT OF ORDER, I APOLOGIZE &THANK YOU! Lynn C.