My guinea pig wont eat?

Question
It has all happened so suddenly. My guinea pig has stopped drinking and eating voluntarily. He also seems to use the bathroom on himself and seems to have no control over his bladder. This being said, I gave him a bath a few days ago and noticed, that well, his anus was swollen so I kind of squeezed it and alot of poop came out (solid).

I have been feeding him orange juice through an eye dropper as well as some water. He mostly just sleeps.

He used to be full of energy and make a lot of noise, even a week ago.

He has always had hair loss since I got him. Not that he's bald or anything, his hair just falls out easily.
His usual diet is oranges, lettuce, weeds, and timothy pellets.

He also is VERY lethargic, his eyes goop up and he wheezes alot.

Can you please help me?

Answer
Hello Kellee.
I can give you the recipe for a syringe fed pellet mash food as orange juice does not have enough nutrients and could actually be worsening the problems. Hair loss like that is normal so cross that off the symptom list. I can tell you that I cannot find any one answer for you about what is wrong, but it is internal and may need surgery, please ask the vet about surgery as it is upsetting for me to talk about as I just lost one of my guinea pigs. You can pick up a syringe at the vets office, preferably well you are taking the sickly pig in, this might save his life as he is very very sick right now.
The hard poo poo might be a case of not enough fibre. Make sure he has hay in his cage.
The eye crust could be an upper respiratory infection (URI) and would also explain the wheezing.
The bladder problems could be a very bad urinary tract infection (UTI) or bladder cysts, bladder cancer or a bladder stone. These are all quite serious and do not pass on there own.
The anal swelling could be that something got stuck and then infected, he had a cut and it got infected or his UTI spread and swelled up the area.

PELLET MASH
Soak 5-7 pellets in a small dish of warm water for a half hour.
Replace warm water and microwave for 7 seconds. Or heat on low in saucepan for 1 minute.
Mash pellets until liquid, adding more water if necessary.
Put in syringe and gently and slowly release into guinea pigs mouth, .1 at a time.
Do not force the guinea pig to accept it.

VEGETABLE MASH.
Soak 5-7 small chunks of lettuce in a small dish of hot water for a 15 mins.
Replace water with tap cold water and microwave for 7 seconds. Or heat on low in saucepan for 1 minute.
Mash lettuce until liquid, blender it if necessary.
Put in syringe and gently and slowly release into guinea pigs mouth, .1 at a time.
Do not force the guinea pig to accept it.
(PS: It took me a failed attempt before I could get this one right, but the guinea pig liked it more)