There really could be several reasons. First of all you need to drink lots of water. When the stool gets dry you have to strain more, and it can be painful. Also spicy, hot foods can cause the veins of the rectum to dilate and can cause pain. You need to increase fluids, increase fiber in your diet and try to eat fruits and veggies. If the pain persists, you need to see a doctor.
Drink more water and butter so It will slide out easier.
Maybe you sit on the toilet to long or you could have hemerroids(you get them from straining or sitting on the pot to long).
I don't know may be you eat spicy things or maybe your poo is to big or the pot is to small
Lay off the kfc nigga
You shouldnt be doing it from behind... Or you eat to much.... Or you ate to much hot food... Or could be many things