Do you think I might have AD/HD or what?!

So, I have noticed I have had a terribly hard time in school lately (I'm in 9th grade).. I can't concentrate, my mind wonders or I just talk to the people next to me. I have to be told what to do like 10 times before i actually get what i'm being asked or understand what it is i need to do. And i get VERY frustrated easily, especially when the teacher is trying to help me I just wanna scream and give up. I am trying my best to get good grades, but it's really hard when I can't concentrate or understand what i'm doing. I don't know what the symptoms are of AD/HD or ADD or anything. So what do you think I could have? Thanks.