This could very well be anxiety related. I would also like to remind you that sometimes minor issues can affect our body, and these minor issues are not serious concerns at all. We don't tend to consider that a minor benign issue could be affecting us, we tend to automatically begin to focus on the most serious things we can consider. But sometimes things like diet, nutritional deficiencies, colds, flu's, stress, things in our environment, lack of a good sleep schedule, and those sorts of things can affect us.
For whatever reason, my body began to go a little berserk when I was 17. I don't know what set it off, but I was suddenly having high levels of anxiety, panic attacks, waking panic attacks, bumps in my throat, painful tense chest pain, feeling of weakness, feeling like I was going to faint. I felt like I was just going to fall over and collapse. However, I was in general pretty healthy. Still to this day I'm not quite sure what set me off, but thankfully after I got some tests and I was ruled healthy, my body began to relax and things went back to mostly normal.
I think that the best things you can do are:
-eat a good diet with a wide range of healthy foods fresh foods
-do moderate exercise consistently
-sleep on a regular schedule and get your zzzz's.
-find an outlet for stress relief (art? meditation? dancing? therapist?)
-don't assume the worst; realize that HA people have a tendency to focus on the the most serious scenarios they can think of, quite often irrational scenarios that are unlikely... you can break this habit by keeping your focus on the positive side, which I think is more likely and probable anyway.
-trust your doctor's judgment.. you may have a few other tests, but if they turn out normal for the most part, you should relax and trust their judgment and realize that it could be anxiety or other benign things.
Feel better soon.