I have had the same problems you had for quite a while and I've come to understand what they are. I have GERD and my blood pressure is a bit high for my age (only three years older than you actually!). Anyway, the point of this conversation is that I went to see a therapist and she explained to me that since no doctors can find anything wrong with me outside the symptoms I just outlined (and those associted WITH them) that I come to expect my problem and so mentally, I bring it on myself.
Perhaps it is not all in your head, but try eating a meal once or having an entire day thinking that nothing is going to happen. Joke with yourself about how stupid it is to get worked up over it and try your best to actually laugh at yourself. If your mood improves, you just might find that you've brought it on yourself.
What someone said earlier though is *VERY* true ..the mind is a powerful thing and it can bring on all kinds of stuff, including digestive and heart problems. If a cardiologist cannot find anything "wrong" with you I would suggest what I said above...you might just save yourself a lot of time and worry.