I'm 27 yrs old, i've hypo tyroid, under medication for the past one and half years, consuming thyronorm 25 mg in the morning..i work in night shift, i take this tablet in the morning and then i sleep. now my periods are regular, but if i forget to take tablet for say two days, again i find tiredness, not able to tolerate cool environment, puffy face..kindly advice me, do i need to take the tablet life long, will it affect if i'm trying to get pregnant, what should be the range for T4 and TSH normally?