Are you just stuck with the inherited mindset that monogamy is the default choice?
Or are you just afraid you will die alone because you haven’t invested in creating a supportive community for yourself?
Or are you just scared of opening up your heart to more intimacy and being vulnerable with other people than just your romantic partner?
Or are you just believing that holding on tightly to the one partner will prevent them ever leaving you?
It’s always good to inquire honestly what are your motivations for any type of relating, and sometimes it can be both an adaptation and orientation. The exploration is what gives you deeper insights into yourself.
If you aren’t sure, coaching or therapy with a qualified and experienced practitioner can help.