Why there is gases after intercourse?

Some time if intercourse is perform with the female in the all fours position, (doggy-style) the anatomical way the penis is inserted can cause air buildup in the vagina which will be released shortly after intercourse a.k.a. (queef). If you are talking about yourself having gas as the male, then that could be explained as you triggering your parasympathetic nervous system allow the bowels to to relax and expel gas. This is nothing to be concerned about.