Bi or just curious???

I love my SO very much I jokingly brought up having a 3 sum with another girl and him but he shot it down real quick, why?? Don't most guys want a 3 sum?!? It's a dream come true for them!?! As the years pass with us being together I love him even more but I'm still curious about being with a female, it's not that he isn't enough for me in bed, I just want to experiment a little, but if I see him even kiss another girl I'll get jealous I just know it,I think I want to be with the girl while he watches??i know I'm not lesbian I love the dick!!! Idk need advice please!!!