Is he coughing, like he needs to clear something from his throat or is he coughing and somewhat out of breath? The only thing I can think of that would cause a response like that is an asthma attack. Physical exertion can cause an asthma attack. (Asthma attacks do not always cause a life threatening inability to breathe. They can sometimes present as a coughing fit or wheezing.)
Does he have allergies or asthma?

thank you,but,no he doesn't have allergies or asthma. And he's not coughing to clear anything.... he coughs and more less gags and like he's going to puke.It's like it makes him sick or something after he cums

Strangely enough, I found a lot of similar posts where people threw up or felt like throwing up after orgasm. Unfortunately, no one had a solution to this problem. One site suggested that the orgasm- which causes various muscles to spasm- may actually cause the stomach to tightly clench and cause the urge to vomit. Sorry I could not find a treatment for this.

have a question, after my gf and i have sex i usually caugh, like clearing out my throat and like my throat is really dry.. what could have caused it?