Law is determined by any standard the country wishes to use.
Theft, Murder, Rape laws exist in every country are about well being.
Sex laws, drunk in public, indecent exposure like laws are also legislated depending on the country not based on any arbitrary standard but according to what is accepted as decent by a country or state.
I can't see how you're being immoral.
As it relates to any conduct sexual or otherwise, you say it is not immoral if it causes no harm to other conscious beings.
You also say that conduct is immoral when it harms other conscious beings.
I have shown that legislation in every country on earth governs human actions that affect others.
You say that morality exists because you feel concerned about harm to others whether or not legislation governs such action. And you also feel that concern whether or not the law says it is legal or society says it is acceptable. Is that your proof that morality exists?