Our 14 year old daughter had nearly identical symptoms and we went the same route as you have (psych doctors, meds, etc.) initially, but my sister stumbled upon another miserable mom who listed her wide array of symptoms also exactly as those that her son who was diagnosed with PANDAS. The top of our list was severe separation anxiety, followed by OCD, tics, mental anguish and ADHD, extreme sensory issues, the urgent need to use the bathroom often, and the list goes on. It has been a nightmare and I could write 3 books, but in short, she has been on a high dosage of AmoxClav for over 2 months and all of our lives have improved. We, too, were told that we would only get a 2-week rx for antibiotics from our Chicago doc, but we can not immediately afford the IVIG treatments and we were not going to leave her in limbo. While there are no doctors around us who treat PANDAS, we found a NP that is a total believer and prescribed antibiotics for us until we can afford to move forward with IVIG.
I agree that you just have to listen to your "mom's intuition" voice and go with what you feel works best for your daughter. Good luck to you and keep us posted.