Hi Nothing is wrong with you. The female organ, that is vagina is specially designed for sexual intercourse. It has a balance of lubrication, tightness, adaptation and so on. The oral mucosa, that is mouth is not so, as it is designed for other purpose. So, there is variation. At your age, the level of sexual stimulation will be very high. Even for people above 25, there can be premature ejaculation, as u have. You need to give more time, get established in sexual act ( there is no substitute for experience) before thinking of medical help to manage your problem.