Iam 24 Yrs Old.my Tsh Level Was 26 And T3

Iam 24 yrs old.my tsh level was 26 and t3 ,t4 was normal in august of this year.physician prescribed me to take 25mcg thyronorm for one week and continue 50mcg .after one month I chckd tsh and t3,t4.it was normal.again physcn told me to continue to take this for 6 months.is this necessary to take for lifelong.because now iam facing wght loss and tiredness moreover bckpain..having a good diet itslf.. iam not healthy..what should I do..