Is doxycycline the antibiotic they prescribed? It is most effective against tick diseases, but in very short supply and very expensive right now. When I needed it for Cabo a couple years ago, it was only like $40. My sister had a dog with a tick disease shortly after that, and the doxy was super expensive so the vet gave her minocycline which was cheaper. And it did help him. Maybe your vet could go that route? Or you can sometimes look at compounding pharmacies I think, to maybe find doxy a bit cheaper. An antibiotic is really needed to help the Lyme symptoms.