@kiera people are trying to help you, but are left wondering what to say or do to help.
There have been many things going on lately, many changes, new additions and I suspect that will not stop. With each new pig comes a new challenge as they, being very much individuals, will react differently to things. Although we feel that Prince is reacting to his new situation by not eating or drinking much, and although this is not uncommon, I understand your fears that this may be due to illness, not just to fear of his new surroundings. I also understand that you didn't at first recognise that Jack was ill and you don't want to repeat that (though please don't blame yourself or his neuter for his tumour - these things are unpreventable). I know you are worried.
What people are struggling with is that you come for advice, you receive it, then you change your mind, and it all becomes quite difficult.
I realise also that you do not make all of the decisions regarding the guinea pigs, so this leaves you wondering what to do for the best, and that you swing from one opinion to another with all of the influences from here and elsewhere, and your own fears mixed in.
People try to help, and then feel they hit a brick-wall. Does that make sense?
Firstly for Prince you have a decision to make. Do you rehome him to a forum member? Do you keep him as a single pig (not the best option) or do you neuter him?
Let's look at the pros and cons.
Neuter:
Pros:
Will get to live with sow/s and express his natural behaviour
He should have a pre-op examination where you can discuss your concerns about the op AND about his eating and drinking
Cons:
You may find the post-op period stressful, and therefore so might he.
You may find not all in the sow herd accept him so may have to change the groups around.
Either way I would normally suggest taking him to a vet to discuss the eating and drinking. HOWEVER
@kiera I think you need to write down what has been going on and included everything. Include the fact that he is new and where you got him and when. Include the things you have done to help to settle him, include the amount of times you've handled him, include his environment and any noise levels in the household and close proximity to other pigs and to people. Give your vet a big picture, the full scene, else he may misdiagnose Prince.
Rehome:
Pros:
You mentioned you wished to do this. Now you don't. Now you feel you never could, but if you feel out of your depth with Prince's health or behaviour then personally I feel you shouldn't feel guilty about deciding to do so, to one of the members here who have kindly offered. He would receive vet care if that is what he needs, and everything else and it would relieve you of the stress you are feeling with him. I'm quite sure anyone here would be happy to update you of his life and progress, and you will no longer have all of this stress.
Cons:
You would miss him for a while, but as I say, you could always enquire after him and get updates. You would never be left wondering if he is OK.
Remember
@kiera, for anyone to help you best, whether it is on here or at the vets, the more details you can give, the bigger view of the whole picture that we have, the better we can help you. Try not to disappear when people are trying to help, even if you are feeling down and finding it hard to post.
I am assuming you are very young (12-14 maybe?) & maybe he was bought as you were very determined to get another & your Mum relented? I am guessing totally here & I apologise if I am wrong. Are you weighing him? I am concerned you have a piggy that because he doesn't eat is going to either go into gut stasis (A medical emergency) or he will be too weak to survive his neuter next week. We can't always have what we want, it's one of life's lessons unfortunately. I have recently had to give up my piggy as she needs frequent dentals & although I have been really upset I know she is better off with some company of her own kind. It is better to do what is in his best interests, rather than what you may want as it's kinder in the long term.
