Hi, I had an open bypass in May. The left side was painful for me for sometime, and I still think I feel twinges now! 3 weeks is early days. I was told to walk each day, but certainly not over-do it. It takes longer for the internal wounds to heal - 9 weeks I think they told me. If in doubt contact the hospital that did the surgery and try to speak to the bariatric nurse.
Above all take it easy, this is really invasive surgery. x x