Our family has a lot of experience with this. Your gut bacteria might be out of balance and you might also have food allergies. My daughter and I both had this problem. She was worse than me. We have been treated and are much better now. We were treated by an alternative doc. You might want to google "leaky gut syndrome".

The only symptoms that I had for my food allergies was reflux, constipation, hemorrhoids and stomach pain.

My daughter finished treatment and was cured when she was almost 6. Afterwards she told me "mom, my stomach doesn't hurt anymore!" She had been in pain since she was born.

Have you heard of probiotics?