I have difficulty paying attention?

I am 17 and I don't know Why but I have a hard time following instructions. I have mental retardation and I can't understand what is going on around me. I always want to do my own thing and I just seem to make people so pissed at me and ticked. Other people like my step dad will get realty angry at me when I don't do what he says and I go off to do my own thing. Kids at school will often yell at me and tell me I'm not doing everything right. I have been telex at my whole life from other people that the way I am doing something is not the correct way to do something. People will yell "DUDE, YOU ARNT DOING THAT THE CORRECT WAY!" I usually get a facepalm reaction after this and make people angry at me. I have been told I was stupid or an idiot because I can't stay focused. Lately my junior year had been full of people correcting me and it pisses me off. Am I the only one like this? The reason why I say I'm retarded island because everyone thinks. I am. Sorry for bad spelling was using mobile version of yahoo answers.