Before it can be fixed, you need to find out what is causing it. Go see an movement specialist, PT/ATC, Osteopath/DO, etc to get your body assessed and movement patterns analyzed to determine where the problems are located. Could be a pelvic tilt issue, could be a leg length discrepency, could be a hip rotation deficit, etc.
If you are concerned enough about it to post on a message board, I would assume that you are concerned enough to find and go to somebody who can give you an in person evaluation and get on the right track. Once you determine WHAT the problem is, the rest should be easily fixed.