nhsdirect.co.uk
Try your local library or book store, they have a medical encyclopedia for children and adults but I want to stress that these are great books but in know way take the place of a doctors medical advice. If you are unhappy or unsure of a diagnosis or lack of, then I'd suggest getting a 2nd opinion
Good luck
nhsdirect.nhs.uk/ you can try this site they also have a phone number to call,ive used them in the past and they really helped.
a book called the physician's desk reference it can answer any question about any known medical condition and symptoms
If you like reading ,then you must consult a book on pediatrics.
The complete book of medical symptoms in children
by Martin B Edwards can be found in your local library
Go to web md, and type in what you are looking for.