If he is only taking ciprofloxacin for a few days he would be al right to carry on with doxy and roxi, but I would think it too much for longer than that. Apart from metronidazole, David would never prescribe more than two abx for me at any one time. I hope he get over it soon, poor thing.
Good news about the new MRI: I seem to remember you saying that the original damage was in the spine. My guess is that once the UTI is over, the current problems will start to get better because any kind of stress really throws you off balance. It still does with me.
Of course, I won't mention the physio!!
Sarah