Heartburn or heart attack?!

So I’m probably only 4 weeks pregnant right now and I know heart burn can come at the end of pregnancy and I’ve been pregnant before I had no heartburn that whole pregnancy and my baby came out with a full head of hair. Tonight I felt a tightness in my chest I eventually fell asleep. I then woke up in pain and jumped up and that’s when my heart felt like it was being stabbed and squeezed at the same time I could barely move I’ve never felt anything like it I was home alone but my 6 month old was sleeping I was so worried about having a heart attack and no one being there for him I called 911. By the time they arrived it was over but my chest still felt sore they did an ekg and said it must be heartburn. But could heart burn really feel like the end of the world like that? I’ve never ever felt something like that. Could it be due to pregnancy even though I’m only a few weeks? Any past stories would help