If you have a thyroid issue, it can make you gain weight no matter how hard you fight it, but when you are being treated and your levels are normal, you can lose the weight you gained.
If you are truly working out and eating healthy you will have more energy and you will lose the weight. If you are still dead tired and not losing the weight ask yourself if you are HONESTLY giving it your all. If you are, demand that your doctor have ALL of your levels checked and get a copy of the lab results so you can see them for yourself.
If your levels are normal then maybe you aren't trying as hard as you thought. Thyroid issue or not, it can be hard to make the lifestyle changes needed to become fit and healthier, but once you do, you realize how much better you feel and look.
As far as the lower carbs... (thyroid issue or not) You just need to find what works best for you. Mine are usually on the lower side but that is because they come from veggie/fruit sources, not the packaged "middle aisle" foods.
farahb7, Congrats on all you accomplished!