If you are in committed relationship and positive to each other then you may try this injection which reduces sperm count for shorter time and when you want to back to normal you can do it.
Professor Richard Anderson, from the University of Edinburgh, who is heading this research found that when a mixture of testosterone and female hormone progesterone injected twice a month that leads to temporary lowering in sperm count and when discontinued it come back to normal level. Normally it stimulates brain to lowers those hormones that involves in maturation and secretion of sperms.

This method is only useful in committed relationship and canít prevent to sexually transmitted disease so it is not an alternative to physical contraceptive devices and will use in those people which is minimal risk of diseases and in which female, no other contraceptive drug is useful.