It sounds like a herx, but I'd suggest calling your Lyme doctor (use the "after hours/urgent" phone number) to make sure they know what you are experiencing.
I know the ER is scary and can sometimes be frustrating, but if you get worse, it might be better to go and get help rather than trying to wait it out...they can give you anti-nausea meds and hydration, and whatever else you might need to get you through this.
Do you do any detoxing? It might help to reduce the severity of your herxes. The "New to Lyme" thread has suggestions for detoxing...
Chronic Lyme Disease, Bartonella (clinical dx only), Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, etc.; G-Tube; TPN via PICC (trying again to wean off the TPN).
Meds: IV Cipro, Heparin (to flush PICC line), Singulair, Claritin, Domperidone, Colloidal Silver, probiotics, digestive enzymes, Milk Thistle & other liver support herbs, Magnesium, homeopathy.