Sternum Pain & Shortness of Breath

I am 28 Years old, I have been experiencing extreme pressure/pain in my sternum with shortness of breath. I have been cleared of cardiac, and pulmonary factors (EKG, XRAY, CT, Holter monitor, echocardiogram, stress test, etc).
I feel as if I can take a deep breath because of the pressure in that area. Its not caused by anxiety ot asthma. I also have pulsations occassionally in that area.

I did have a barium swallow xray done to r/o hital hernia, which came back negative but found a moderate amount of acid reflux, which my gastro said is mostly normal for everyone to some degree. My primary thinks it could be acid inhalation but this seems to be unlikely. Acid reducers, and taking protonix for a month, no difference in size of meals, before or after eating, etc so I doubt the GERD theory is the cause here.

Also I have been off of klonopin for 3 weeks (low dose 1/8 Mg) so not sure if that is a factor with the shortness of breath.

What else could be causing the pulsations in sternum besides the esophagus.

Thank you,
Matt