About the ham sandwich - I use an online food diary (Nutridiary) to calculate the amount of calories in my food. A lot of people here use Fitday, which is also good (and free). I always take the calorie counts on packaged foods and enter them into my "foods" category. That way, there isn't as much guesswork. A slice of bread can vary between 70 and 150 calories per slice! Also, it depends on how much ham you use, that's why I think portion control is so important so that you know how much you are really eating.
A ham sandwich could be 150 or 450 calories, depending on these variables.
There are lots of on-line calorie counters or you can buy a calorie book if you don't want to do an online food journal.
Good luck in your weight loss efforts!