Nibbles101, please also ALWAYS remember that Guinea Pigs are, by nature, prey animals and while they may not be to such a degree in our homes as they would be in their natural environment... think about it, prey animals "put on a front" and pretend they are in perfect health, run and jump around so they wont LOOK sick and in pain and be picked of for that reason by a predator - until they are so ill they just cant do it anymore.
To be honest, a vet check-up and treatment is not that expensive when you compare it to the value of your pet's life at all. I mean, we pay £15 for a pig to be seen and more often than not, another £5/6 for the treatment. That's it! The only time we've paid something higher like £40 was for neutering. You could at least take the pig to be seen and then make an informed decision on it. Obviously everyone one here wants to help and is therefore telling you to take the pig to the vet - which is absolutely the correct thing to do and the correct advice to give you but we cant make you or your parents do anything.
If you won't take it from us, as fellow Guinea Pig owners, then please take my word for it as a Zoologist, I know what I am talking about, I have been taught about this kind of stuff and I practice it regularly, as do the other people on here and all we want to do is help.
I must also agree though that any pet's welfare is the LEGAL responsibility of the parent. BY LAW ALL pet owners MUST provide each and every pet with each of the 5 Freedoms.
1. Freedom from Hunger and Thirst - by ready access to fresh water and a suitable diet to maintain full health and vigour.
2. Freedom from Discomfort - by providing an appropriate environment including shelter and a comfortable resting area.
3. Freedom from Pain, Injury or Disease - by prevention or rapid diagnosis and treatment.
4. Freedom to Express Normal Behaviour - by providing sufficient space, proper facilities and company of the animal's own kind.
5. Freedom from Fear and Distress - by ensuring conditions and treatment which avoid mental suffering.
Those who do not provide these can and have been prosecuted in the past. It is that important. I'm not trying to scare you or bully you into taking my advice and the advice of the others here - I'm just trying to help you see that what we are saying is in the best interests of everyone, especially your pig.
I sincerely hope you do take your Guinea Pig to a vet asap... if not, that's up to you but even if you gave up the pig to someone who could take him/ her for treatment, wouldn't that be better for the pig? - Just make sure they know what they're letting themselves in for if that is the route you take.
Please think about it at least.