The odds of having a heart attack at your age, without any genetic factors (immediate family problems ect) is ridiculously low, so I'd put that out of your mind and system. You've been tested a year ago, so you're fine in that regard. Remember, even people who have known heart problems, or who have had previous heart attacks, only typically go through testing once a year. It's unlikely your heart has changed that much in so short a time. That's not even discounting the fact that heart problems are more commonly discovered through exertion than rest.
What it could be, possibly, is indigestion. You've said that your eating habits are not good, and something such as Acid reflux or IBS could very much be a possibility. Anxiety itself can do crazy things to our bodies. You could even have breathed in a little hard without realizing, felt breathless and panicked, leading to the other symptoms :)