I am 24 years old. Since a few days, I sometimes feel a little tightness in the chest when I try to go to sleep. I also feel the same sometimes during work, which sometimes affects my memory as I find it hard to recall what was recently said (this happens very rarely). Thinking that it is a cardiovascular issue, I got it checked through ECG and BP immediately (got checked a month ago), the doctors said everything is fine. But while sleeping, my focus automatically shifts to my heart rate which drops when I am about to sleep. This makes me anxious and I have to wake up. What is the problem here?