Concerned about persistent dull ache in left chest (3-4 months)

Hi. I've scoured the Web for information that might help me self-diagnose, but haven't found anyone describing quite what I'm experiencing. I'm not prone to anxiety, but I have had an exceptionally stressful year at work - combined with too little sleep. Some nights I have had as few as 3-4 hours of sleep, but for the most part I get 6-7 hours of sleep. My heart region started aching during periods of acute stress about 4 months ago. It is never intense. It's just a dull, persistent light ache. I am a runner, and there are times when running vigorously increases the pain ever so slightly. But it's never anything approaching acute. I have no trouble breathing. It just persists as a dull discomfort. I took antacids, but that had no effect. It has always been fairly localized on the left side in the area of my heart. It does not radiate to arms, shoulders. 

My father - who is 72 and very healthy lifestyle - had a bypass operation this past year due to calcification from persistent flow turbulence due a defective valve. So I suppose there is some genetic predisposition to heart disease. But I'm 42, and I'm not experiencing anything acute. It's just that the dull ache doesn't ever fully dissipate. Should I get it checked out? Or should I just relax and work less hard? Anything for an excuse :-). Advice appreciated. Regards,