First I would suggest talking to your doctor to rule out any changes in your digestive tract health. There are several possible causes for your symptoms and I am not a doctor. Until the cause is found for the abdominal cramps, I would suggest not eating these foods.
Second, most of the foods you mention are gas forming (broccoli and cauliflower). Corn sometimes is not digested well by the intestinal tract and the hull can pass through intact. Green peppers can cause burping as the skin needs bile from the gallbladder to be digested. It may be that you just overdid the amounts of these foods at the same meal.
After your doctor has ruled out any physical cause for your cramps, burping, and gas, I would suggest you slowly add these foods back into your diet, one per meal and in small quantities (1/2 cup). You can increase the quantities slowly (1-cup), then try mixing two at the same meal. You will find your individual tolerance to these fresh vegetables.