I vote for sleep. I eat really well, drink a lot of water and go through spurts where I exercise regularly. Been doing this for the last 3 or 4 years and whether I am exercising or not, I was always dead tired in the morning.
My girlfriend got a new job that required her to be up earlier in the morning, so we both starting going to bed an hour sooner. I used to go to bed between 12-1am and we switched to 11pm, no later. After switching, I was getting up on time for work and had plenty of energy.
Just recently, she got switched to a later shift, so I started staying up late again. 12am to 1 am every night. Once again, I am dead tired every morning. My alarm doesn't even wake me unless I keep it across the room. Trust me, your problems are mostly sleep related.