Hi I Am 27 Yrs Old And Recently Married, And

Hi I am 27 yrs old and recently married, and I had a sudden weight gain, and so I had visited a Doc and she suggested to get a pregnancy test and as well as TSH test. My reports suggested that I was not pregnant but my TSH was 15 and so my doc has suggested to take 50 MCG of Thyronorm. Would this be a long term med that I need to take and will it affect my child bearing ability as I am planning for a new born ?