One thing that may have made you feel better right after the surgery was IV steriods they gave you during surgery - they last for about 3-4 weeks and then wear off.

I did the same thing after my thymectomy - I felt great even though I was in ICU - could breathe the best I had in several months. When I commented about it to the nurse, she kinda laughed and said it was due to the IV steriod (can't remember the name). She was right - I went back to my "normal" self after about 3 weeks!

Hang in there!