Unfortunately, the risk is a part of showing your images on the web for as soon as you put images up anywhere they can be stolen. Every time someone goes to a webpage their computer puts all the images in their temp folder for example and most browsers nowadays completely ignore the "no right click" code we do have in place. Besides which, anyone who visits can screenshot the pages.
However, your full images are nowhere on this site, only low resolution copies. Anyone who wishes to steal your images will do so even with watermarks and would not buy them. We have numerous posts about this in the discussions area. Visit there and put 'watermarks' in the discussion search