If heart and GI are ruled out, that leaves muscular.
In the thread that GenSec pointed to you, both of us found that cardio/stretching helped a lot. I did a hard spinning class yesterday and I'm feeling pretty damn good today with very few pains.
I'm going to guess your shortness of breath is due to the anxiety created by the pains themselves. I would tell you to get checked with a doctor to be sure, but you've done that, so if it is muscular, try:
A) doing cardio every day for a week (and continue if it helps). assuming your general health is good, you'll be able to work up a sweat and be even more assured that you don't have cardiac issues. on top of that, it really does seem to help the chest pains for some reason. perhaps the endorphins or just the fact that we're built to exercise and our bodies need it. do chest stretches and hold them for longer than 20 seconds.
B) Zazen (mindful meditation). It's astounding how many anxiety issues can be resolved with this one, and it can even help the real physical symptoms. You just sit somewhere, don't worry too much about posture, but keep your back straight. Don't worry about quieting your mind, because that won't happen. Just breathe from the diaphgram and count each breath. You'll start to hear your brain chattering, and that's normal. The minute you start to get distracted by it, start back at 1 and continue counting your breath. do this for 10 minutes a day. Not sure where you're from, but mental health is something we really overlook in the US. Meditation and mindfulness is like going to the gym for your mind. You won't get a six-pack from one visit, and you won't overcome your anxiety with one sitting. It's a practice.
C) Get a massage. This is on my to-do list as well.