I think you need to understand what having a monogamous relationship means.
mo·nog·a·mous məˈnäɡəməs/ adjective involving marriage to one person at a time.
having a sexual relationship with only one partner at a time.
having only one mate at a time.
Sounds like you want a polyamorous relationship:
Polyamory (from Greek πολύ poly, "many, several", and Latin amor, "love") is the practice of or desire for intimate relationships with more than one partner, with the knowledge of all partners. It has been described as "consensual, ethical, and responsible non-monogamy".