stop taking thyroid pills ?

I was on  thyroid pills for about 3 yrs because I had an underactive thyroid and I was told I would have to take them the rest of my life, but  my doctor took me off of them about a yr ago said  my levels werent low enough anymore, and since  then i put on about 20 pounds  and feel like crap again ,  is it normal to have your doctor take you off thyroid pills, because everyone I know  that is on them says no  I should still be on them ?????