3month ago my Dr put me on 50mg of levothyroxine which too my thyroid level from 5.4 to 1.7. I fell pregnant and at 4 weeks went in to have my thyroid tested again. It had rise to 4 so after much encouragement my Dr put me on 75mg. I unfortunately miscarried at 6 weeks however my Dr told me to keep taking 75mg. I had my levels checked again yesterday and im down to 0.63. What I want to know is, what is the optimal thyroid level range for fertility. Is 0.63 too low? Should I be lowering my dose if my Dr refuses to?