Why am i feeling jittery so later in the day? 10 points?

Well if you've never had coffee before and today you had some, that can possibly have triggered you jittery. Some people can't handle caffeine that is found in coffee. I highly doubt it's your change of diet. If anything it should make you feel better or a little bit more energetic for eating healthy food. So I'm more for the caffeine as of cause than processed food detoxing as you called it.