Please see a vet ASAP!
Both ear infections and e.cuniculi can kill of left untreated. It is up to your vet to diagnose and treat; they may want to treat for either to be on the safe side.
You may need to see a specialist if you don't have access to a piggy savvy vet. We can only guess and help you ask any questions you want to ask a vet but we can in no way replace a vet. Any head tilt needs to be adressed as quickly as possible; the longer you wait the more difficult it is to revert and the higher the risk that it could be permanent.
The longer you wait and DIY treat at home, the greater the chance of losing your piggy or having a fight for life and death on your hands.
Here is our vet locator:
Vet Locator
If your piggy is not eating and drinking much, you also need to step in with feeding and watering support.
Bridging and crisis care support advice to keep your guinea pig going until treatment is kicking in fully:
Emergency, Crisis and Bridging Care until a Vet Appointment
Please be aware that the heat wave in the coming week is an additional killer; your piggy needs to be in the coolest possible place and be kept as cool as possible.
Heat stroke and hot weather management:
Hot Weather Management, Heat Strokes and Fly Strike
Please take the time to read the detailed advice and tips in the various links. They can make the difference between life and death as no medication can work if a piggy is not getting the necessary home care support in terms of daily weight monitoring, support feeding care and being kept in the best possible surroundings during extreme weather.
Fingers firmly crossed - I hope that you have been able to get an appointment for today or have had your piggy already been seen.