Cut out all fizzy drinks. That alone will make you loose 15 lbs a year and help your metabolism. Also things like ranch and mayo. That's where the unnesisary carbs come in at.
Hi there.... Since you have hypothyroidism, the first thing I'm going to ask is that you make sure your thyroid levels are right for you. Even though they may be within the reference ranges, they might not be high enough for you to be comfortable.
The easiest programs to stick with, are those that let you make lifestyle changes that you can stick with from now on. I don't think I'd ever be able to do atkins... while some carbs are not good for us, some of them really are and should be included in a healthy diet.
The main things to do are to make sure you get plenty of lean protein, lots of veggies, which are basically "free" (meaning you can eat all you want, as long as they don't have fattening sauces, etc). Switch from products made with white flour and sugar, to those made with whole grains.
Keeping a diet diary is also a good idea, because that let's you track everything you put into your mouth.
Have you calculated the number of calories you should be eating each day?