“Panic attack advice?”

Hello not sure if this is the right place but, about a month ago I was super stressed and I think it caused a panic attack, I felt like I was dying and it was terrifying. I went to the ER and they did an EKG and told me things looked okay. They gave me a paper that said the diagnosis was an anxiety disorder and the reason for visiting was heart palpitations, that night that it happened I felt like my heart was beating super quick and after the visit and after I calmed down. I had sharp pains in where it felt my heart was. It's been about a month and I've been calm but I've had shoulder pain and neck pain and sometimes when I rest I get this sense of uncomfortableness and I feel like I need to move or turn over and massage my shoulder/back area on my left. I'm curious if it's just the anxiety that's making me feel like there's still something g wrong but I feel like there is. Currently, yesterday and today it felt like the opposite where I feel like I didn't have a heartbeat and I had a weird lightheaded for a sec. I was hoping these would go away by now especially the pain on my shoulder it feels tense. I was wondering what I should do.

Basically,
I had a panic attack a month ago, since then I've been having shoulder pain on my left side and more recently lightheaded feeling and it feels like a really low heartbeat which concerns me but I am unsure if it's the anxiety/panic attack talking but it feels like somethings wrong I was wondering what I can do or what I should do.