Funny I was juz reading some stuff about tiredness some minutes ago,
Ive been falling asleep at my laptop as well but it was because I hadnt have much sleep because of uni works. I suggest you to talk to a Counsellor, they're always helpful with their advices.
Your feeling of tiredness and change of eating habit might be because depression (You can always talk to some professionals to feel better and you know that what you tell them is confidential and they dont have the right to tell other people). Try to have healthier foods, exercise and have a bit of fun

get out of your room and go outside and feel the sunshine on your skin, breath the fresh air and look at the green nature, listen to songs and dance as if nobody's seeing (for this part you can do it in your room! haha) Be happy!