To my knowledge, hypothyroid should not prevent you from getting pregnant if you get your thyroid function back to normal.
It really should not impact your ability to get pregnant. I have been hypothyroid since the birth of my first son 4 1/2 years ago and have had one other son and am now pregnant. HOWEVER, while pregnant you should have your thyroid checked very frequently and most people end up taking more replacement toward the end of the pregnancy. also, low thyroid can make it more difficult to breastfeed (in both of my son's cases my milk just dried up even though I was exclusively breastfeeding and pumping constantly) and can exacerbate post-partum depression. All of these things should be prevented though by a good doctor closely monitoring your levels. Good luck!