Obligatory: I am not a doctor, I don’t know your life.

Jumping off the other comment suggesting a low-fodmap diet, do you have other health problems? What sounds like an extremely unbalanced diet (possibility in combination with a round of antibiotics or an episode of food poisoning) may have resulted in a condition called SIBO (small intestine bacterial overgrowth), specifically an overgrowth of methane-producing bacteria. I’d recommend getting tested.