I got my instrument rating in new R and SP models and recently have done some instruction at a flying club in an a couple older 172s a K & M models, and I have to say I prefer the feel of the older ones for maneuvers. They seem lighter on the controls to me. Different 172's feel different (even going from one SP to another they can feel different).

There is nothing wrong with you. It probably has a different feel to it. But, I'm betting a lot has to do with the only having one flight in the past 4 months, you really lose a lot when you're not flying on a regular basis. I had to take a 3 or 4 month break in the middle of my private pilot because of a knee injury and it set me back at least a good 8-10 hours. I'm assuming that the aerobatic flight was for fun, and probably a lot less pressure to perform than your normal lessons.

Also, can you go up with a different instructor? IMO, If this CFI really has that kind of attitude you don't need to be wasting your money on him.