Forum:I cant shoot enemy players

I just bought battlefield 3, and went into an online game straight away. But when I tried to fire at someone my character only fired about 2 shots and went prone. Wtf is this shit? I thought maybe I had clicked crouch, so I changed the controller lay out. But no. Becuase even if I accidently clicked melee, I didn't click the right button to make my character go prone. When I aim and shoot at a wall or something it is fine. I bought this game from amazon for not much money, did I buy a bugged game or something?