How Can I Prevent Anxiety and Keep Calm During Stress?

Hey there, I've never used an app like this, but maybe someone can help me. I have been experiencing heart palpitations, loss of consciousness, chest pain, excessive sweating, overheating, and nausea for a couple of days after taking Paroxetine for about a week for my fibromyalgia. I stopped taking it per my doctor and 5 visits to the ER in 3 days. I also have terrible anxiety, and a fear of heart attacks since my grandmother passed young due to it. I was told my heart sometimes beats in the wrong place, and have inverted waves on my EKG. I was told my arrhythmia is not serious enough to cause concern for a heart attack, however, I have a appointment with a cardiologist to check the electricity and my heart function. I've noticed I get anxiety once my heart starts beating what I feel is too fast with pain in my chest, and I'll feel extremely cold while turning pale. I have tried everything including relaxation, increased water, pumping fists, sometimes I'll even take a lukewarm shower. I haven't been to work to cut out all stress, and I haven't been able to exercise for 7 months due to the fibro. Sometimes, it feels like I give myself an anxiety attack due to the chest pain and palpitations. What can I do to prevent the anxiety from building? How can I keep myself calm when my body feels stressed? Thank you for any and all advice you may have.