I Get Pressure With Gas Build Up In My Bells

I get pressure with gas build up in my bells and have to go to the toilet to release the pressure like 4 or more times in the night and I'm so tired by morning from so much broken sleep. I'm a 63 year old very fit and health concious male . Health is my no 1 focus! I dont drink or smoke or take any type of drugs no refined foods or refined sugar little meat take alot of flax oil and do alot of walking and gym twice a week. can't expell air apart from toilet stop. a dry mouth during the night and each time I get up I have to take a little water. Can you help, thanks!