I keep going on about this lately, but you should get your thyroid levels checked. Difficulty losing weight and fatigue probably rank in the top 3 of hypothyroid symptoms. Susceptibility to infections, including yeast ones, is another. Standard check-ups may include a check of your TSH level, but this is a pituitary hormone, and doesn’t reliably show thyroid function. If your T3 and T4 levels are in a good position within range along with good TSH, then you can probably rule it out. It’s quite a poorly diagnosed/treated condition, and as a result you might need to practically coerce your doctor into diagnosing your with it by learning about it yourself. I’d hope it’s not an issue, because it require lifelong medication, but that’s another reason to make sure it’s not an issue before getting your hopes up about improving your health naturally.