My resting heart rate is increased. Am I at the risk for a heart attack?

Hello doctor,

I am a 23 year old male, who is fit and active. I do not drink alcohol or take illegal drugs. I smoke about 15 cigarettes a day and drink some coffee and tea, about two or three cups a day. I do not like energy drinks, so I never take them. I am not on any medication. About three weeks ago, I started a new job. As one of the requirements of the job is to get a medical test done, I failed in it as my heart rate was 140 bpm at rest. My doctor checked it thrice to ensure it was right. He checked my heart rate again over the next week and looked at my blood test results too. The lowest my heart went to was 85 bpm but mostly it stayed at 100 to 95 bpm. He said he could hear a heart murmur. I did not have this previously.

I do not know if this is related, but I was told I sometimes wake up at night gasping for air, in a sudden manner. I do not have any nightmares as much as I can remember. Other than that I feel sick often. I do get stomach cramps about two to three times a week. My doctor sent a letter to the hospital for more tests. He does not know the reason for high heart rate. I might have to wait for a long time to get the tests done. Is there anything I could do while I wait? Also, my father had a heart attack when he was 45. Could this be a sign that a heart attack is waiting in later years? Should I even be worried or is this just normal routine checks? Would love to hear from you. Thank you for reading this.