Hi
Your dog needs a full clinical examination in order to make a diagnosis. She could have a metabolic problem, a musculoskeletal problem, a neurological problem - it is impossible to tell without examining her.
You could take her temperature with a rectal thermometer, if it is >39C then that would suggest she has an infection of some sort...if she is in pain, then aspirin is a semi-effective painkiller, half a tablet given with some food. However, I would urge you not to self medicate but to brave a trip to your vet, they should be sensitive about your cost concerns.
Good luck