i have an underactive thyroid also. i was diagnosed after i had my first child, probably had it before. i took clomid to get pregnant. the first time took 4 cycles, the second 2 cycles, the third 1 time. i also have polycystic overies, so i was dealing with 2 things. i carried to term with them all. had no problems. its just important to have your levels checked while pregnant. i took the lowest dosage of clomid all three times, even if you don't have insurance it's affordable. i think it was maybe $50. before you start trying chart your temperature to see if your ovulating, if you are you probably won't have much trouble getting pregnant.i was on 125 of synthroid when i got pregnant with my last baby. good luck.