You might want to send your doctor to the ILADs site when you are trying to get more doxy:
ILADS.org said...
Increasingly, clinicians recommend that certain drugs used for Lyme disease be given at higher daily doses: for example, 3,000–6,000 mg of amoxicillin, 300–400 mg doxycycline, and 500–600 mg of azithromycin. Some clinicians prescribe antibiotics using blood levels to guide higher doses. Close monitoring of complete blood counts and chemistries are also required with this approach.
With higher doses, there may be an increase in adverse events in general and gastrointestinal problems in particular. Acidophilus has reportedly reduced the incidence of Clostridium difficile colitis and non-C. difficile antibiotic-related diarrhea.
Serious adverse effects of antibiotics, however, were less common than previous estimates. In a recent clinical trial of chronic Lyme disease, the overall serious adverse event rate was 3% after three months of antibiotics, including 1 month of intravenous antibiotics. Clinicians who have experience with higher dose antibiotic therapy must balance the benefit of higher drug levels achieved with this therapy against the modest risk of gastrointestinal and other side effects.
Here is the link. Read this page because it gives a lot of helpful information.
http://www.ilads.org/lyme_disease/treatment_guidelines_clearing_ilads.html