Why would sex outside of marriage be considered sex work? For something to be work you need to receive some sort of material compensation. Usually it's just money. But I guess if someone gives you a car or some jewelry in exchange of sex it could classify too. I don't see how having sex with someone in a party where both people wanted it could conceivably be considered sex work
Human trafficking is already illegal. Fund investigators and get rid of traffickers.
Empower sex-workers instead of banning the practice, because it will still happen but just more in the shadows. Bring it to the front and truly regulate it.