I recently (within the last 30 days) have had very scary incidents, or reactions to stress. This included a tightening of the heart muscle, some light nausea, and a headache on both sides of my head. I was in Denver so I thought it was about family stress and the altitude. I have been living the last month or so at about 1000 ft. above sea level. The attacks were so severe I had to lay down, which didn't help, and too several hours to subside. I took alleve but it didn't seem to help very much. What is this and what can I do to prevent it?