Constant lower GI discomfort and pain please help?

Never really have the urge to deficate, always have to strain to poo, sometimes almost p out while deficating. Excessive, and i stress excessive gas. I take lots of fiber and drink lots of water. I haven't tried heavy laxitives, light laxitives don't work. Always feels like I have a bowling ball in my stomach. What is this? These symptoms came on very suddenly and have persisted for about a year. I am thinking about having a colonoscopy. What do these symptoms manifest? Educated advice only please.