Hi Priya,
It would help if you could post your calibration images. From what you've written it sounds like your cameras may be too far apart.
The first thing I would try is to run rectifyStereoImages with the OutputView parameters set to 'full'. See what that looks like.
The next thing I would try is to move the cameras closer together.
The reprojection error of 0.6 pixel is not bad, but using more calibration images never hurts.