Bloating, stomach pain, gas that smells like sulfur, and bowel movements. What's causing this?

Many possibilities. A plethora of possibilities exist. You could be lactose intolerant,in which case avoidance of all lactose-containing foods should really help (primarily dairy products). If you have well water, it may need to be tested for contaminants, including parasites such as giardia (other household members may have similar symptoms), were this the case). I would try a reputable probiotic and see how you do.