As to the thyroid, effects differ significantly from person to person. Some have no idea they have a problem until it shows up in a blood test -- my wife had that happen to her. Mostly she was suffering from things you would attribute to a problem with sexual hormones, but it turned out to be the thyroid, so there you go. As for the weight gain, you don't mention exercise at all, and the only things you mention you eat, and I'm sure you eat a lot of other things, are things nobody should eat more than very occasionally -- soda and chips. But basically, you need to start exercising regularly to compensate for sitting around all day.