My 8 year old chihuahua has to be on a prescription diet due to colitis (irritated stomach and intestines/colon) he won't eat some days and just does the "burying" and I have to take bits of soft food and put it in the back of his mouth and hold his mouth shut until all dog food is eaten. Some days he loves his food, though. It's more often than not that he won't eat but on days like yesterday where he won't eat, I wake up to bloody goop that he has pooped out... If I don't force feed him I feel like he will die. What is going on?

Sounds like your dog is having episodes.

Call your vet

From my understanding of colitis, during an episode you are to fast the dog for a day than gradually start back onto food with a bland diet. This would be browned hamburger and rice or boiled chicken and rice with all fats drained as best as you can. Feed this for several days then slowly start to introduce the hard food.

But. If your dog is having lots of episodes, call your vet and maybe a recheck is in order

Bless your heart. My Yorkie was just diagnosed yesterday with Colitus. I freaked out because when I came home there were 3 circles of blood in the kitchen. No feces. I grabbed him up and took him to our vet. He said it was Colitus. He had a small amount of blood a few times before and I was alarmed but thought I would wait and see. He also has had very loud gurgling at times that could be heard across the room. He has never liked dog food. We feed him boiled chicken and used to give him table food. NO MORE of that. Vet gave him a shot for immflamation and an antibiotic shot plus 2 antibiotics to take for 10 days. I took off work today because I did not want him to be alone. If he was mine I would take your dog back to the vet and just tell him or her that he will not eat and has no appetite. Good luck. Hope all turns out well.
Scooters Mom