I can relate to this somewhat, but it happened to me while I was on Zoloft and one of the reasons I came off of it. After about 2 years on it, I felt like I was always on the verge of a panic attack, one that never materialized and it gave me anticipatory anxiety. This was the major reason I chose to get off the Zoloft. I now have full-blown panic attacks, but have had made really great progress using CBT tools to stop them. It takes a bit longer than a xanax and demands my full attention, but hopefully I'm rewiring my brain to not have them anymore.
I also get bouts of vertigo and had to come to the realization that dizziness doesn't mean something bad is happening. Something very silly, like allergies, can cause me to become dizzy. It's really challenging sometimes!