Had a followup with my primary care doctor yesterday, after the tests he had run a couple weeks ago. Breathing test and EKG looked normal, but he noticed the rapid heartbeat that was measured three times in the two days I wore the Holter monitor. Those happened, like today, after eating. I don't get the symptoms EVERY time after eating, just randomly. Breathing test was "normal" because I wasn't in the process of working around the house or taking long walks, the only times I get short of breath. The days I need to be somewhere and mom doesn't feel like driving, I just don't eat that day until I get home, to be on the safe side.
Primary care doctor said he talked to my surgeon at the hospital about those occasional symptoms after eating, and she told him it's likely tied in with the "dumping syndrome" a lot of people get after the type of surgery I have, and that not much can be done about it.