Has anyone been prescribed an SSRI/SNRI that made you feel much worse?

Long story short, I visited another cardiologist yesterday who prescribed Cymbalta low dose slow release for dysautonomia relief. I took one pill and the next day I feel like I've suddenly developed POTS.

Several weeks back I was prescribed Propranolol and took one pill of that and the next day my exercise tolerance plummeted

Is this all just coincidence or is it possible that we do not react appropriately to certain types of medications?

I fear this change much like the last one is going to stay with me long-term 😥