tpup, please do whatever you need to see a knoweldgeable doctor as soon as possible Infectious disease doctors are not usually the best to see for tick-borne diseases unless they specialize in them. You have not been treated aggressively enough or long enough. 500 mg of Ceftin is too low of a dose to treat Lyme disease. Three weeks of treatment does not even cover one growth cycle of the bacteria.
Have you been tested for the co-infections? This is very important. Many people who have Lyme are co-infected, and it can affect treatment choice and progress.