Hi and welcome
I am very sorry for your loss. It is nothing you have done wrong; it sounds like a stroke or a heart attack to me. Sadly some piggies come with a genetic time bomb in their bodies that can go off any time and age.
Young guinea pigs can be very sensitive to irritants and hay or other dust, which is what you and your vet would be looking at if a couple of courses of antibiotics don't help (just one week may not be long enough) but these irritants are not usually fatal. The symptoms you are reporting are not that of a pneumonia, which could have arisen from an undertreated respiratory infection.
Irritants to Avoid Around Guinea Pigs
Unfortunately since you are not intending to help us with your location, I cannot tailor any advice re. resources available in the country or general area you are in, seeing that we are dealing with enquiries from quite literally all around the world and from extremely different backgrounds, climates, vet and rescue access, different medical and supply brands etc. All these considerations will go into any recommendations and ongoing support we give. As a result, our individualised advice can vary quite massively depending on the location and availabilities of the particular member. The less we know, the more basic and general the advice will be. We do not recommend anybody to post their exact location for their own protection; nothing closer than their county/state/province or large city.
For instance, in the UK we do have 24/7 clinics or special out-of-hours vet services which you can contact asap at any time of the day or night whenever your local vet clinic is closed. In other countries this is generally not available.
We have bundled all the necessary information into one thread to help when you are in a panic. It is worth knowing that this is available if you are a UK resident and worth finding out where your closest service is.
Here is our emergency advice access link:
Emergency, Crisis and Bridging Care until a Vet Appointment
Does your piggy have a companion since guinea pigs are group animals and are not wired to live alone? Please look after them to make sure that they are OK. As long as they are still eating and drinking (i.e. not pining acutely), they will usually keep for about 1-4 weeks re. finding them a new companion unless they can really not cope well with being on their own at this young age when they are still in the formative weeks and relying very much on the guidance of the elders in their group.
We recommend to look for a new friend at a good welfare standard rescue with mandatory quarantine/vet care, proper sexing etc. that offers dating at the rescue in order to achieve the all important personality match, provided you can get to any - this varies enormously around the world or even a country.
This is even more important with sub-adult boys to get the pair safely through the teenage months. Most people unfortunately buy their piggies for their looks and not for who they hang out with most which then makes for a miuch more difficult teenage with a much higher risk of fall-outs.
Please be aware that we can only guarantee for you being in safe hands with the carefully vetted listed rescues. Anybody can call themselves a rescue or breeder without licensing and control, and results can be accordingly.
Here is our rescue locator (which you can also find on the top bar together with our recommended vets locator). We cover a number of countries. Unfortunately we cannot give you any recommendations which ones would be best to contact first for your purposes:
Rescue Locator
You may find these guides here helpful in finding a character compatible new companion:
Looking After A Bereaved Guinea Pig
A Comprehensive Guide to Guinea Pig Boars
If you'd rather purchase a new baby companion on spec, then you will have to always bond them on neutral ground outside the cage. Guinea pigs are territorial and see others as intruders so you cannot just stick a new piggy into the cage and expect them to get on. the bonding process is also more complex and takes a lot longer (on average two weeks post-intro) than most people expect. Our detailed illustrated bonding guide will take you through all stages and aspect step by step so you can understand what is going on at every stage.
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
Please be kind with yourself in the coming days. It is very normal to have strong feelings of guilt or failure resulting in some major soul-searching whenever a beloved one dies; but they tend to be stronger in the wake of an unexpected or traumatic death. Guinea pigs have huge personalities which covers the fact that they are actually very small prey animals that can go downhill very quickly, especially as they are wired to hide any symptoms . By the time you see symptoms, they are already seriously ill or even dying.
Here is our human grieving guide that will help you to make sense of your feelings and experiences right now and in the coming days. We have also included a chapter that helps you with tips and resources for helping your children through a loss, depending on their age.
Here is the link:
Human Bereavement: Grieving, Coping and Support Links for Guinea Pig Owners and Their Children
If you feel a strong need to understand better your experience of the dying process etc., then this guide may help you to make more sense of them:
A Practical and Sensitive Guide to Dying, Terminal Illness and Euthanasia in Guinea Pigs
