our guinea pig is ill?

  our guinea pig wont eat and will only move if we make him. we are worried about his weight, he was a pretty good size, and now hes getting skinnier everyday. my sister is heart broken. we have had him for about four and a half years. my mom says we dont have enough money to take him to the vet and even if we did its a guinea pig, and why waste the money.: (I have no clue what to do, I dont want to see him suffer .
You must take your piggy to the vet; he probably has a problem with his teeth, so he can't eat as well as he used to and needs his teeth trimmed. Your mother is being cruel by not taking him to the vet, it is not a "waste of money". I would suggest taking him to the vet, and then saving the money for your guinea pig's care by not buying your mother any more birthday or Christmas presents, because that really would be a waste of money. What kind of an example does she think she is setting you and your sister? Not caring for an animal is neglect. At least you are responsible. Explain to your mother it is her duty to ensure that your pet has the proper care that he needs.
Your mum has a terrible attitude. She is letting a poor little animal suffer. It sounds like he will die without the urgent medical treatment he needs. You cannot look after him alone. Your mum should never have allowed you to have a pet if she was not willing to care for it when it is ill. You need to force your mum to take your guinea pig to the vet as it is clearly in pain and suffering and it is so cruel just to leave it. If you cannot do this then give it to an animal rescue centre were they can nurse him back to health.
I get so very upset with the mind set that guinea pigs are disposable pets, just let hem die and get a new one after all it is just a guinea pig. Man what stupid thinking, this is the little animal who has given you all its love without hesitation, without question, it has just loved you, comforted you when you were down, but it is just a guinea pig so let it die don't spend $ 70 or $ 80 bucks to get it well, Oh no it is just a guinea pig. I have been know to spend up to $ 1000.00 on one guinea pig and she was worth every dime , she was they one true friend i had in hard times, the one that did not run away, the one that stood beside me through thick and thin as only guinea pigs can do in their special little way.Your family has no business having pets if you are not willing to provide proper medical care for them, it saddens me so.
i agree with all the other comments. but one of my old guniea pigs died like that. his teeth grew so long he starved himself to death ... that may be the case but its a lot of money if you bring him to the vet (it can range from100's and maybe even 1000's) i know its hard to see them go but they dont last forever: (its just that guniea pigs dont really show that they are sick, only like close-to-death sick. sorry: ( pets question and answers,www.5d2d.com

good luck!
I hate to say this, but i think your guinea pig is getting close to the end of his little life. If mom wont go to the vet, there is not much to do. Make sure he has clean water and food, and a warm place to sleep, and just wait to see what happens. Your sister is really gonna need you to comfort her if the little guy dies. Good luck to both of you.