First of all, tantric sex is a form of magickal practice. It is used to change a situation, changing thought form into reality. It has nothing to do with sexual pleasure. In fact if you are receiving any sexual gratification, then you are not performing tantric sex. You have failed!
Second, there is a lot of background work that needs to be done, such as perfecting meditations, focusing energy and thoughts. It takes many, many years of mystical practice to be able to use this type of thought control. Most people never reach this stage of ability. You must have a partner who is at the same level in her/his mystical or magickal abilities, and your partner must be focused on the same goal. Both of you must concentrate on that single goal the entire time you engage in sexual intercourse. That means no stray thoughts of an orgasm that leads to something pleasureful...just the end product being the creation of the thought form reality.
If you want to try to practice this form of magick and you are a beginner I suggest that you start a rigorous meditation schedule. I also suggest that you have a life long partner who shares your same goals before you even consider entering into this type of magickal practice.