I've looked high and low for fixes to my problem but have come to the conclusion that I am just not able to word my searches correctly, or that I have a very specific problem.
Anyway, what I am trying to do is create a human figure from a cube by extruding out and scaling down many faces to create a curve that fits my background image.
The same effect happened on a quick mesh I made for hands, feet and the groin area. This means that the problem is definitely due to how I am making the 'slits' for those areas.
I've no idea how to go about fixing the problem as everything I have tried has failed miserably.