scared!

Angel
I got diagnosed with under active thyroid at a early age of 14. A top consultant at the time advised me my ovaries may dry up around the age of 30 and if I wanted children to bear that in mind so I did. My now husband and I got together when we was 18 and 6 months into the relationship I told him I had to have children young because I couldn't risk getting older and loosing my chances. Anyway against the pill on a tummy bug I got pregnant with my first.. a year later had a miscarriage 10 weeks in and was devastated so we tryed again and got instantly pregnant... then a couple of years after her I missed 1 pill!! Got advised to take the pill through my 7 day break to stop the egg fertilising and found out I was 9 weeks pregnant a couple of months after.. I had the implant for 3 years.. had another fitted when it was due but after 3 months of having it in decided to have it removed and try for one more.. I'm now 29 in November. I had extreme ovulation pains for the first time ever for the first few months.. then the last 2 cycles were barely cycles and this month I haven't even had a period and testing every morning staring at negative tests. I went and discussed with my doctor that I feel something isn't right and he sent me for blood tests to see if I ovulated last month.. no egg realeased and my thyroid showed perfect 2 months ago and now had to lower my dose as it was slightly high! He wants me to do another progesterone test this month and another thyroid one next month but I haven't had a period so how am I meant to know when my day 21 is?? How am I meant to know if it was a completely missed period and judge the next one?? Could my ovaries be drying up?? I'm so scared out little family so desperately want another baby. Xx