Not everyone wants to settle down, whether to live with someone or get married and have children.  Do what your heart says and be true to yourself.  You are still young.  You may think and feel differently as the years go by or meet someone that changes your mindset.  People don’t usually want to settle down until they meet someone who fulfills all or almost all of their desires and expectations.  Some think that living life “to the fullest” includes loving someone and being loved and having a family.  Being the human beings we are it is difficult to be as you say, “locked down” to one woman (or man for a woman).  It is part of human nature to want to be with different sexual partners.  That is why people cheat.  But when you love someone and all is going well, it pays to control your desires for other partners to keep that loving relationship.  On the other side of the coin, there are women out there that believe in an “open” relationship and perhaps that could be for you.  You probably have never been in love and when you do fall I think you will feel differently.

Sincerely,