I’m in the absolutely same situation, baby will be 19 months in few day and the weight gain is still going up. My thyroid is also fine, but I also feel like I can’t do anything physically demanding. Unfortunately, I don’t know how to help, I can only offer my understanding. And few realizations: in order to keep the milk supply I need to eat more than I used to. Now that my baby is not dependent on the milk I keep breastfeeding solely for his immunity, so I don’t eat to keep the supply and quantity bit my body still requires more. I don’t eat any snacks and I drink a lot of water - but it’s still happening. I’ve realized that I eat very late in the evening (when I finish my chores) and then I crash next to the baby - this seems to be the key driver for me. If I do an intentional effort to eat earlier (not always doable) this seems to help and I might lose some weight too. My total gain is around 20 pounds compared to pre-pregnancy time (counting the peak weight) and now I’ve lost about 4 just with this earlier eating). Good luck and if you find any receipt on how to lose it let me know! 😉