First, it sounds like you are doing fantastic!. Everyone is different!Congrats! I'm 5 weeks tomorrow and started Cardiac Rehab this past Friday.
My 3 struggles at this point are
1) Musculoskeletal pain in the chest as my muscles, nerves, and whatnot are trying to come together.
2) Getting my lung capacity back. I can get my spirometer to 2500cc right now. But that's my current limit.
3) Pretty tired most of the time.
How are you doing with those 3 things?
My walking is good like yours. I'm doing 2.5+ miles a day.
This is my second open heart surgery, and this time has been easier than five years ago for whatever reason. Don't worry too much about where you are. Just keep doing what you need to do, and you'll keep improving.
Where I'm currently at four weeks out:
1) Pain control is manageable with acetaminophen. I'm taking 3300-3600 daily on schedule, and it hurts pretty bad if I'm late. I've been off the narcotics during the day since week two and just took my last little pill at night. I'm not asking for more.
2) Spirometer is up to 3500. I was at 4000 before surgery, so I'm getting close. I need to do it more, as I've been slacking.
3) I'm also tired. I'm trying to get more sleep at night and take a nap every afternoon. I'm not always successful at those and pay the price.
For context, I went into my surgery in great shape. My docs attribute that to my quick recovery, even beginning in the OR. They extubated me and woke me up in the OR rather than the ICU because I was doing so well, something they rarely do. I was also sitting in the chair five hours after surgery, and it sounded like that was a record or close.
After my first surgery (also in great shape), I wasn't up in the chair until the second day, and it was a horrendous experience. Getting to the chair the first day was unthinkable. Moving to the chair the second day was so painful my heart actually stopped from bearing down! When I came to, there were like 30 people in the room and a crash cart open in front of me. A little epinephrine in my swanz ganz catheter and cranking up the external pacemaker got me going again. Good times!