From my experience (and from what I have read, others) an SSRI should help your anxiety, not make it worse. I know the first week was a little hard for me, but they gave me some ativan to help ease me on to the medication (prozac). I recommend trying it. It sounds like you do indeed have PPD on top of the POTS. PPD is very dangerous if not treated so I would start your SSRI as soon as possible. Don't be scared, any medication can give a certain percentage of people a bad reaction, but it is not common. I've left many doctors offices crying so I understand. I'm sorry.