When I eat certain foods or drinks my stomach expands n I look like I'm 8 or 9 months pregnant n I have abdominal pain. What causes this.

Uncertain. At age 49, with significant abdominal distension, and intolerance of certain foods and abdominal pain, you really need an exam and likely imaging of your abdomen and pelvis. This could be anything from a bowel related problem to an ovarian cyst.