Hypothyroidism and Euthyrox...help!!!!?

I was diagnosed with hypothyroidism last year.My doctor gave me Euthyrox 50 mg,then I went to 75 mg and then to 100mg as my blood tests are always wrong and my TSH is low....when are the levels of TSH going to stabilise??? is it normal that I have to increase my Euthyrox levels so much???