Your thyroid could certainly be a cause. Not all thyroid problems are going to respond to the supplements you are taking. I would get a thyroid panel done to see what my hormone levels are. You may need something like armour thyroid to boost your levels. Also, have you tracked your calories to see how much you are actually eating? If you are eating the same amount of calories that you're burning each day, you are not going to lose, no matter how healthy your diet it.