First, you are definitely
not an 'evil person', I have done something quite similar (I don't have POTS, however I do have extreme anxiety.) I of course at the time felt terrible about it, however I hadn't done anything to fix that -which now I deeply regret- perhaps try to talk it out with him, tell him your concerns. That way, he can help you through it. I haven't necessarily told anyone my concerns, (including not liking to go to parties, because I don't want to get anxious.) And, due to this -no one knows it makes me uncomfortable, so they continue to take me- what I am trying to say at this point is, reaching out to someone you trust, (my grandma is the one I trust the most, in which I normally tell her about my concerns.)
Will allow them to help you push through this.
Don't fret, everyone just needs a helping hand every now and again!
__________________
There are many types of monsters that scare me: Monsters who cause trouble without showing themselves, monsters who abduct children, monsters who devour dreams, monsters who suck blood... and then, monsters who tell nothing but lies. Lying monsters are a real nuisance: They are much more cunning than others. They pose as humans even though they have no understanding of the human heart; they eat even though they've never experienced hunger; they study even though they have no interest in academics; they seek friendship even though they do not know how to love. If I were to encounter such monsters, I would likely be eaten by them... because in truth, I am that monster.
-L (Death Note, Tsugumi Obha)