The premise of a "bulk" is that you eat a caloric surplus so that you have the energy to build muscle, however excess energy (which we measure in calories) gets stored into fat cells. So all thats happened is you have gained an excess amount of fat cells, to remove these cells, find your maintenance caloric level (The Big Sleeps question above is going to help you find that out) and then cut that by about 10% to help you not chew up muscle but keep you on a caloric deficit to help you bring back your body fat percentage so you can see your abdominal muscles again. Things to help you from your body using muscle as calories is to eat around 1lb of protein per pound of body mass. The increase in protein also helps your internal thermogenic effects and will help you burn a few extra calories.
If you decide to do the cut, best of luck.
Philippians 1:21: For to me to live is Christ, and to die is gain.