If you are talking about sex with another person, it’s most certainly a privilege.
The issue is that it requires another person, and if we live in a culture that recognises the idea of consent and rape, then you need to convince another person to have sex with you.
You can convince them in a range of ways. The easiest, obviously, is being born with an appealing genetic makeup. There is paying them, either as a prostitute or offering a cushy lifestyle through your own wealth. You can work out. You can develop your personality, tell jokes. You can just work really really hard to support and attract them.
You could argue in abstract that sex is some kind of human right. Tell a bear you have the right to life while it is eating you. Tell the deer that you have a right to food, so it will lie down and let you cut it’s throat.
You have the right to nothing.