Still short of breath at 3½ months out?

Greetings all. Long story long...LOL

Back on Sept. 24th, I had quintuple bypass surgery done. The surgery overall went OK, but over the next couple of days, I aspirated and they had to intubate me two separate times. I spent the next 7 days in the CICU and then 15 days in a 'regular' room before being discharged. Once home, I was still using O2 at 1L per hour. After just a couple of days I managed to get off O2 throughout the day but still used ½L O2 overnight. I managed to get off O2 completely after about 7 days. The ongoing problem I've been having ever since being released from the hospital is I get winded so easily doing just simple things like walking across the room and bending over to put my shoes on. I've been going to cardio rehab at my local clinic for the past month and a half, and that's helped me regain my overall strength and balance but hasn't helped me at all with my shortness of breath. I should also mention that when I was first set up at home, my resting heart rate, even at night, was mid to upper 90s. After the first month or so of rehab, that did settle down to the low 70s, but now after the last couple of weeks, it's crept back up to the lower 90s. I guess my question/concern is, is this ever going to get better and if so, what's a realistic timeline?

I should also mention PT2: I did have a spirometer sent home with me and I did use it a lot for the first few weeks, but since I've just gotten myself to take deep breaths and hold it W/O using the spirometer. I guess I look at that as I'm accomplishing the same/same with out without the spirometer, right?