Can drinking protein shakes stop me getting a six pack?

Yes: You probably each enough protein and these shakes are calories ; make you fat. You're going to need to diet and be hungry for a fair part of each day, and not "reward yourself with food." you'll need to do some serious aerobic exercise. As you lose most of your body fat, start developing your abdominal muscles. Especially, don't neglect exercises like cable pull-downs for heavy resistance.