last night my puppy (six weeks) started coughing... i was not to alarmed but then at about two this morning he would wake up and start do breath hard like he had a hair ball or something. he would cough and pretty much choke. then he would go right back to sleep like nothing ever happened. he did this three times last night and once while i was getting ready for work this morning. i checked his mouth and made sure he didnt have anything in his throat or stuck in his back teeth and there was nothing. he stays in a crate and there is nothing in there small enough for him to swallow. when ever he was out of his crate i had my eye on him the whole time and he never got into anything. does anyone have an idea of why he is doing this??