It was about two months after my MI I got back on the bike, with prescriptions for anti-platelet, beta blocker, and statin. Riding five miles back and forth on a flat, deserted street had me heading back to my recliner for the next two days.
Two years later, I'm regularly commuting by bike (10 miles each way) and doing weekend rides of 50 miles plus. Forty pounds lighter, two years older, 2,000' accumulated climbing isn't unusual, but I'm not as fast as I once fantasized I would be if I took off that weight. I'm still on the beta blocker and statin, and I enjoyed a cycling vacation of 420 miles in a week last summer. (With a couple passes.)
Your system had a heckuva shock. You've been off the bike for six weeks, deconditioning for that time. You're not the 21 year old stud kicking sand on the 97 pound weakling any more. Be kind to yourself. While I'm sure you'd rather walk out the door tomorrow morning and pick up where you were six weeks ago, you're going to have to rehab your body. Treat this as an experiment of one to see how far you can go (in a metaphorical sense) from where you are now. Six months to a year out you can look back and see how you've progressed, but right now you're too close to start those comparisons.