chest pain but it’s not my heart

f19 120 ish lbs. I have no prior medical history. I don’t take any medication. I do smoke weed though (i don’t know if this could be a factor.

I’ve been feeling a bad pain in my chest. it wasn’t consistently at first, it would happen if I laid down and leaned back, I thought it was my bra or the way I was laying so I always brushed it off. that happened for about three days. on the fourth day I woke up and the pain was bad. it didn’t just hurt if i leaned back or laid down it hurt all the time. the pain was in my chest in the middle of it between my boobs, maybe on the top of my rib cage bones (??) like pressure, like someone was squeezing something in the middle of my chest. I went to urgent care because I really thought it was the end of me!! they gave me a ekg and told me it wasn’t my heart but didn’t even really give me any answers when I asked them what else it could be. I have a doctors appointment in the middle of september but I just want to know if this is symptoms for anything? should I be super super worried? everything else about me is normal, just the tight squeezing pressure in the middle of my chest.