What could this pain be???

Ok so as I was breastfeeding my newborn earlier, I had a sudden pain on the left side of my chest. I had to give my newborn to hubby while I worked through the pain bc it caught me so off guard with how painful it was. It hurt every time I took a breath. I took a deep breath in and suddenly felt like something popped and the pain disappeared. I did some research on google and thought it could be something called precordial catch syndrome? Anyway, so a couple of hours later I started feeling some dull pain in my left shoulder and upper arm. I’ve been feeling it for the past hour or so. I’m just afraid it could be a heart attack. My anxiety is through the roof right now. :(