What Causes Discomfort In The Upper Chest Area?

I think I may have angina. I have had about 3 episodes in the last two weeks that started with an increasing bad feeling in my upper chest that intensifies. My husband gave me nitrastat the last two times; however, I don t know if it was the reason for the easing of symptoms or that it went away just as suddenly as it started. I would appreciate any thoughts. Last year I had an ablation procedure which cured my tachycardia, if this may have any bearing on the problem.