Having practiced tantra, non ejaculatory orgasm and various methods of bodywork there is a small advice to give. A fundamental area to give awareness to is the instinctive drive towards ejaculation as opposed to an open ended state of conciousness to your experience and your own sensations. This leads to more energetic awareness and creates space for the orgasmic energy to be experienced more and more fully. Dont try to block or hold the orgasm forcefully. The game changer is to be able to relax in to the feeling and not get carried away with the unconcious impulse to contract in to ejaculation and release the energy through the penis that has built up. It is also possible to block the ejaculation but still release the energy witch maybe is happening to you. The aim is not to release the energy but to let it build up wave after wave. This is done gently, not by force and when you ejaculate, there will be more semen and the orgasm will be stronger, to the extent that you have accumulated energy. It is an exersice in staying concious and your capasity to experience and hold more energy will develop through practice. It takes time and it is a process to go more and more deep in to the practice and trials and errors are part of the Journey. It is worth it!