I had this guy buy me jewelry and because I wouldn't sleep with him he said he wanted it back. Will I get in trouble if I don't give it back?

No.  If he gave you the stuff it is yours; he has no right to revoke the gift.  Even if he gave you the stuff on condition that you would sleep with him, such a contract would be unenforceable as prostitution is illegal in Washington.  Theoretically, if he gave you the stuff on condition that you sleep with him on some trip to somewhere where prostitution is legal, he might have a claim, but I doubt it. Of course, all of this assumes that the facts you've relayed will be believed.  If the guy claims that he loaned you the jewelry, or that you were supposed to pay for it over time and didn't, it is possible that a judge or jury could believe him.