TSH is down to 0.19, but told to stay on same dose? T4 is in range at 9 (Pregnant)

I was diagnosed with Hashimotos pre-pregnancy, but my levels weren't too bad and were controlled with 50/day of levo, which kept my TSH around 2.

My MFM/OB is currently managing my dose, and long story short my TSH kept rising despite continually increasing my levo dose. After my TSH came back at 5 in the second tri (it's supposed to be <3) while on 100/day, I was told to up my dose to 150/day.

I've been running warm lately (can't sleep with blankets or tolerate too much heat in general) so I wasn't too surprised when my TSH came back at 0.19, which is technically hyperthyroid per the reference range.

I figured we'd overshot the dose and he'd tell me to go down a bit, but I got a note to keep on the same dose.

Anyone else have their dose managed like this?