My thoughts and questions, are pretty much along the line of Nancy. My Son (who is now 21) had a pacer and never really felt it that much, if your boyfriend also has a defib and it is fireing that often I would be concerned. Has he told his doctors what is going on? Following my son's surgeries, when he had problems, we called his cardiologist or surgeical team and usually avoided the ER unless there was a big problem in the middle of the night, then the docs would have us go to the ER and would meet us there.
I would definatly be getting in touch with the cardiologist if he is having so many problems 4 months past surgery. Has he had any echos or other tests recently. ARe the breathing issues ongoing since surgery or are they more recent? having trouble breathing COULD be a sign of fluid around the heart or lungs.
Also since he is 26, was he dxd as a child with his heart issues or is this new and his first surgery?
Good luck please keep us post
ps is he walking and doing his other excercises that help with recovering from OHS? This far out, if he hasn't considerred it, he might want to ask about cardiac rehab, so they can keep and eye on him while he is exercising and maybe figure out what the problem is.