I'm not a doctor & I think a medical professional would be better equipped to help you, but I wouldn't think this could be DCS lasting this long.
If it were me, I'd try going to different doctors to find ones who care. (I don't mean a good bedside manner since the great doctors aren't always the nicest ones, but ones who are intent on finding out what's wrong.) I'd also make sure that a full work up was done if you haven't already (full series of blood tests, vitamin deficiency tests, etc.). You could have a couple of things going on where the fainting has nothing to do with the pain. And I'd really urge you to review all the results yourself & ask if you have questions. Doctors can make mistakes. I was shocked to find I was actually badly anemic & needing immediate IV iron transfusions after the doctor's office said I was fine. But what would have happened if I hadn't checked the results myself? I might still be having horrible problems & everyone would be thinking it couldn't possibly be anemia since I had been checked for that already.
It's scary that your neurologist doesn't seem to care about the EEG results. I'd take those results to another neurologist (or 3) & see if they have different thoughts.
I know it can be soul crushing to continuously go to doctors & not get the help you need. (I've been in that exact situation). But you have to push to be your own advocate. Every month, there should be something you are doing to help yourself. If you've only seen 5 or 6 doctors in 2 years, this means you are only seeing a doctor every 4 or 5 months.
I'd probably add in an Internist (assuming that your GP practices Family Medicine. Both are great doctors, but personally, I've had better success with oddities when using doctors practicing Internal Medicine rather than those focusing on families). I'd also add in an orthopedist since as tomcat noted, problems with the muscles & cartilage by the sternum can take forever to heal (this happened with a coworker of mine).
Sending you strength & wishing you the best of luck!