Colon problems help ?

So im 17 and have a problem but im not sure what. So im always flatulating. My stools come out thicker when I wake up then later in the day some what thin and slushy. I get this itchy sensation in my colon near the rectum. it Burns sometimes when I poop too and usually I get this weird pain in my lower colon but it subsides after a while. what could it be? sometimes its hard to poop as well.