Sometimes, nothing comes out of my penis when I ejaculate. Is that normal?

This is called a dry orgasm but it can also be retrograde ejaculation. These two might be experienced in a similar manner but dry orgasms are characterised by having no sperm at all, while in retrograde ejaculation, semen flows back into the bladder instead of being ejaculated out of the penis. This semen is then released with urine after sex. They are usually nothing serious and can be caused by a variety of things, such as diabetes. They are concerning only when one is trying to have children