Turns out the appointment at 15 weeks that was scheduled for me, with the Medical Clinic at the hospital, was, as my GP had thought, to do with my thyroid results. I saw a doctor there today who went over my medical history very quickly but thoroughly, looked at my thyroid results and i told her about the newest blood test results, and she was pleased with my new TSH level. She wonders if perhaps the first TSH reading was a lab anomaly, because my antibodies are low which rules out Hashimoto's, but advised now is not the time to test that theory! I'm welcome to go off the thyroxine once my levels have stabilised several months after birth and during breastfeeding to see if the TSH goes back up.
She went over post-partum thyroid disease, which is where the thyroid can actually go hyper then hypoactive after birth, and that's when i'll need to be monitored as i am now, every 4 weeks, to check on it. She suggested i do one more blood test and then if the levels are stable then one more in third trimester, but doesn't think i need to continue on the 4 weekly intervals. My GP had said that we'd revisit the intervals after my next blood test and appointment with her - i suspect she's thinking along the same lines. The doctor also got me to swallow while looking at my neck, then felt along my neck and said my thyroid was slightly inflamed. I suspect this means that it really was struggling to keep up with producing enough thyroid hormones.
The good thing is i asked the doctor if having treated subclinical hypothyroidism put my pregnancy in a low risk category. She reassured me very quickly that i was very definitely low risk, at no greater risk than any other pregnancy, and that basically it's a normal pregnancy where i just happen to take a tablet each day. I was glad to hear this and hope that my midwife has the same opinion when i have my approval visit on Monday, and that i get accepted into the homebirth program.