Under active thyroid and ttc

I am going through testing as I think I may have an under active thyroid and I’ve been trying to get pregnant for over 15 months now. Has anyone taken levothyroxine and conceived? How long did it take after starting the medication? I know it increases chances of ovulation so I was wondering if this increases the chances of twins aswell? I will be speaking to a doctor once my tests have been done but I would like to hear peoples personal experiences. Anyone that has conceived how was the pregnancy? I have 2 children before I had symptoms of the under active thyroid so I’m not sure if when I get pregnant it will be different I know I will need to be monitored more but is it classed as a high risk pregnancy, like can I still be on a maternity unit and have a water birth rather than being on a high risk unit?