2,000 cal per day for a big athletic guy like yourself would be way too low and would account for a lot of the problems you are having. Males should be getting at least 3,000 cal per day on a high-carb/low-fat diet and the site I trust most says for athletic guys and guys under stress should get at least in the 3,500-4,000 range, so you may only be getting half the calories you need to thrive.
But don't guess. I recommend you download http://cronometer.com
and start inputting what you eat in a day to see how many calories you're actually getting a day on average. I'd really like to see what your macro ratio is too. It will show up on a colored pie graph near the bottom right of the app as Protein:Carbs:Lipids.