Two major things.
BFI--Body Fat Index percentage. For your sake, you don't need a device to know the percentage. You want a sign of abs. So, all you have to do, is stand up flex your stomach and pinch as much flesh as you can on your abdominal area. If you are able to grab a certain amount, you must realize that the layer of fat is concealing the abdominal muscles from showing. Your abs are getting stronger, but you can't see them. In which case, the moment you start losing fat from cardio exercise, is the moments when you will start seeing definition.
The second thing is. Don't bother worrying about the numbers of crunches or situps, they mean nothing. To grow muscle, you have to strain them to their limits and break them down. You're better off increasing the intensity of your abdominal regime and doing less numbers. Try to lay on your back, lift your legs 6 inches off the ground and hold until your abs burn, then immediately try doing bicycle thrusts where you bring your left leg up to your chest while moving your right elbow towards your left raised knee. (Have your hands behind your head)
If you can let go of numbers and go for only your body's feelings, you will be doing much more proficient work towards your progress. Yet again, if you have a layer of fat covering your abdominal muscles, you won't ever get to see the definition but you will be able to feel the strength in your day to day life that requires usage of the abdominal muscles, which includes the lower back when you lift things.
As far as diet, as long as you are burning more that you put in, you are going to lose weight, it's as simple as that whether you're vegetarian or not.