After having intercourse with my husband i get a burning on the outside of the opening of my vagina, it burns only after we have sex what is it?

Many possibilities: It could be a vaginal infection such as yeast, or an std, or even an allergy to condoms. There is also a chronic conditions called vulvodynia that causes the feeling of burning in the vulvar area. It could also be just do to too much friction without enough lubricant. Try using a personal lubricant, such as "astroglide" or KY jelly to decrease friction, but if it continues, see your dr.