You were wise to go to the doctor today and get started on abx. It's typical that a non-lyme literate doctor would prescribe you only 21 days of doxy. I would stay on doxy for at least one month and possibly longer to be on the safe side. By the way, take some probiotics too so that you don't kill off all the good bacteria in your stomach while killing off the bad stuff.
Probiotics are very important to take while on antibiotics otherwise you could develop some serious stomach problems. Take probiotics three to four hours apart from antibiotics. Be sure to eat food with your doxy and don't take them late at night before you go to bed otherwise they'll burn your esophagus. Taking probiotics before bed and when you get up in the morning is a good way to do it.
If you already know this, sorry to repeat it. I had to learn the hard way, so whenever someone gives me good advice like this I always appreciate it.
Razzle, Denise, CajunGrl, others, what say you?