Losing weight with a thyroid problem

I'd strongly suggest reading this thread:

https://community.myfitnesspal.com/en/discussion/10767046/hypothyroidism-and-weight-management

Written by a guy who's a scientist in the field, himself hypothyroid, who lost weight using MFP. Very informative.

What you're experiencing is pretty normal (for anyone) during weight loss. If you're a premenopausal woman, it's even more normal. 😉 Specifically, we often lose a good chunk of weight at first, part of which is water weight. Later, as some of that water weight rebalances, it can hide some continuing fat loss on the scale. Successful weight loss is a long game: Multiple weeks, at least, to see what your weight loss rate really is.

For premenopausal women, hormone-related cycles can add and subtract varying amounts of water weight at different times during the month. At minimum, you want to be comparing your weights at the same relative point in at least 2 different menstrual cycles. I've seen women report cycle-related gains of up to 8-10 pounds, though I think fewer than that would be closer to average.

This would be another good thing to read, so you can better understand what causes weight fluctuations, and how to know whether you're making progress:

https://physiqonomics.com/the-weird-and-highly-annoying-world-of-scale-weight-and-fluctuations

Your best friend right now would be patience. You're eating low calories (assuming they're accurately logged (not a criticism: logging is a skill that takes time to develop for all of us). You're getting exercise. If anything, you may've cut calories further than necessary or desirable. You can reasonably expect to be losing fat. But patience will deliver the answer, over a period of weeks.

FWIW, I'm severely hypothyroid, though properly medicated. I'm also pretty old. Nonetheless, I lost 50 pounds in less than year at age 59, and have maintained a healthy weight for 4+ years since. Hypothyroidism - even untreated hypothyroidism - isn't weight loss doom, as you'll learn if you read the thread I recommended above. If you're not properly medicated, get properly medicated. With that, you should be able to lose weight pretty much like anyone else does . . . which doesn't mean that it will always be easy, that it will be quick, that it will be linear, or anything like that. But if you persist patiently, it will happen.