Also, if you have a coinfection as yet undiagnosed (a disease other than Lyme that comes from the Lyme ticks), then other antibiotics
or combinations of antibiotics
or medications may be called for.
I am not attempting to contradict your MD or give you advice other than what your MD is prescribing, but just want to give you another view. If I were in your situation, I'd be getting myself in to see an LLMD asap. In the meantime, you'll have to decide whether to take the doxy.