Inactive/Sick Mountain Horned Dragon

Question
Hello, I am really worried about my MHD. I bought him in early October, and he went through a bit of a rough spell where he hadnt eaten for a week, so I took him to the vet and got him some parasite medication, and he just finished it last week, and had been doing extremely well all last week. He was much more active, and was eating every other day or so.
 Well I am in college and on the weekends I head back home an hour away, and I leave my lizard at the apartment with a large enough supply of food, running water, and its UVB light that automatically turns on and off every 12 hours. The past couple weekends I have left and came back he has been just fine, but when I came back today he seemed very inactive again. On Thursday I was feeding him and he ate a total of 6 superworms, and I thought I saw him grab a piece of bark in his mouth when he picked up one worm, but I thought he spit it back out. If he HAD swallowed it, could that be whats causing him to act differently? Because usually when I grab him out of his tank his eyes are open and he is alert, but today when I grabbed him his eyes stayed closed completely and he didnt move much at all. It really scared me because he looked nearly dead in my hand so I ran to the bath tup and turned on some water because I thought he was dehydrated, but once he hit the water he really woke up and tried to get out.
 Another thing I was worried about was that when I left for the weekend I also put a towel on a small section of the top of the cage so that it would keep heat and moisture in, but it looks like it got a little too warm, about 80 degrees. Could THAT have caused his lack of energy?
 I think Im going to take him into the vet, but if its something that can be easily fixed I would rather take care of it now (living on a college student budget!)

Thanks and hope to hear from you soon!

Answer
 It's always best to have a vet check.  I would also need to know what you are feeding him and what kind of water source.  If it is a waterfall where the water recycles, you may want to clean it out and disinfect it.  MHD are tropicals and do not hibernate in winter.  So he should active during the day.  Also see if there had been any power outages at your apartment that may have caused him to chill.