Can’t be sure it’s not just joint/muscle pain from my EDS, but I absolutely have arm pain/heaviness that coincides with my POTS chest pain. (Yes, I know that sounds like serious heart attack symptoms, I have been to ER for this and confirmed that that wasn’t the case. Obvs seek emergency care if this is happening to you and differs from your baseline)

Yessss I've been to the ER a few times for this also. No heart attack.

I get aches in my joints but I am not sure if that's due to my hypermobility or the POTs.

The nerves of your arm are directly connected to the nerves of your heart which means when you have heart problems (or POTS) it can cause arm pain. When people have heart attacks they often experience arm pain or numbness as well.

I get bad headaches when I get dizzy