Change your diet. Avoid fatty fried foods and red meat. Eat more vegetables and salads. These leave scarring, which obstructs the path of semen through the penis. If the diseases occur in the testes, infertility results.
Bodywork therapy can help, too.
The PC muscle normally contracts upon ejaculation. By learning to contract this muscle at will, a man can hold off and ultimately intensify his orgasm. The contraction that makes this possible is the PC muscle. Once you are familiar with this feeling of contraction, practice it often to gain control. Make the PC exercise a part of your day.