sorry to hear this. With my GERD/LPR I tend to get chest pressure along the sternum--it is quite noticeable to me and it worsens over the course of the day (best upon waking up). I too did every possible heart test and all were perfect, so it does seem in my case, it is GI related. Sometimes I will also feel slightly short of breath, but I think this is mostly due to worry. I also suffer from PVC (palps)--one doctor told me that it could be vagus nerve irritation which is implicated in breathing, heart and GI issues. My palps were documented on a holter monitor, but not on the stress test or ekgs.
Have you had any GI tests yet or seen a GI? That might be the next logical step--tell them about the normal cardiac workup and see what they say.