Dealing with Anxiety and Fear of Heart Attack

Hey there. Was wondering if anyone could help ease my anxiety a little bit? For the past few months, I’ve had some really bad anxiety about having a heart attack. I’m not sure why, but it’s just a fear I developed randomly. Ever since then, I of course googled the symptoms. One night I woke up abruptly out of a dead sleep with a racing heart, cold sweats and I couldn’t breathe. I since then had heart palpitations at random, and ended up going to the er. They did an ekg and chest x-ray which they said were perfectly normal and that it was just anxiety. Well, now for the last month or so, i’ve been waking up with pain in my left arm every morning, and when I looked it up it said heart attack. What do I do? I seriously feel like this is just a never ending battle. I’m now terrified, again. Is it my anxiety taking over, or should I go to the er again?