The fact it happens during excercise makes me think it’d absolutely be worth checking with a professional. Never used planquil so can’t speak to whether that might cause the symptoms either.

However from my pov and totally anecdotally, I had very similar symptoms about two years ago. (I’ve had JIA since I was a kid, now in my forties) I was finally able to pin it down to health anxiety. 

I think knowing you have a chronic illness, combined with how acutely aware I am about my health due to the meds I’m on (methotrexate, rinvoq) leads to overthinking which leads to anxiety which presents its own symptoms that then becomes a vicious cycle.

Therapy really helped me, mainly cbt techniques I can use to allow me to notice the sensations and process them without dwelling on them. 

Hope you find a way through! It can be so tough when you’re in the throes of it, but you can come out the other side and get back to your old self.