Rocky Seems Sick

Hello,

Rocky (my 12" Rosy Boa) & I could really use some help!

I got him for Christmas, and he was very healthy & active! I have him in a 5.5 gallon aquarium with an under tank heat mat, and a heat lamp with a 75 watt bulb. For substrate, the person at Petco (who sold me the snake) recommended I use Zoo Med Eco Earth Compressed Coconut Fiber Expandable Substrate, he said that is what they lived on in the store, so I bought it.
I put Rocky in his new home & let him settle in for 2 days before trying to feed him a thawed out frozen pinkie. He didn't eat it, so I waited another day. It has been over a week, & he STILL hasn't eaten, and he doesn't look good at all! He looks skinny, he will not eat, & is very lethargic. I noticed a couple days ago that he has mites, so I took out all of the bedding, and replaced it with paper towels, and bought a mite spray from the local pet store called 'Natural Chemistry De Flea Reptile Relief: Kills Mites on Contact', and it seemed to help. I had to use it twice. I haven't seen any mites on him today.

But he still won't eat, I even bought a live pinkie mouse. He is not even interested!

3 days ago, I saw a few small bubbles coming from his mouth, but haven't seen them since.

Please help us! I don't want him to die