If my baby always cries after eating wheat cereal, does he have celiac disease?

Not necessarily. About 1 in 133 of healthy people or 0.7% of the population have celiac disease. About 1 in 56 or 1.8% of people who have suggestive symptoms have celiac disease. So, even in cases of suggestive symptoms, the majority of people do not have the autoimmune condition known as celiac disease. Talk to you doctor about blood tests that can be helpful to screen for celiac disease.
Too vague. Common things are more likely to occur than rare ones.Celiac develops over time as an immune mediated disease,which requires a more mature immune system than a baby.It is rarely found if ever before they are toddlers & mostly in older kids or adults..They can be intolerant to wheat because it triggers indigestion or cramps. They can have a wheat allergy, but that is also uncommon. Quit using it.
Not necessarily. Depends on a few factors - if it's only with wheat cereal, consider gluten intolerance or possibly celiac. Is there a family history? Makes it a bit more likely. Try an elimination diet, taken out all sources of gluten for a week or so - see if that helps. Also - if it does, check with your pediatrician re: testing.
Not necessarily. You haven't told me if your baby cries after other foods. Also, wheat allergy, which is not the same as celiac disease, can cause the same symptoms. It is important to distinguish between the two, as treatment can be different. Celiac disease is diagnosed by specific blood tests. It involves testing for antigliadin antibodies. This is different from the blood tests for food allergies.