It could be the belt, I prefer a 1 1/2 wide if the loops will take it, then again anything that changes how you stand and/or walk even slightly could cause the symptoms you described. I would expierament with the exact placemnet of where you wear the holster, changing position very slightly can cause a big difference. If changing position or belt doesn't help you will have to try various holsters. I have personally found Fobus paddle holsters to be very comfortable if worn in the right spot. Cheap too!
Dave B.