I need advice 😩

Me and my bf have been together going on 3 years now. I love him more than anything in this world and I mean ANYTHING! He knows I'm bisexual and he's okay with that. I mean, what guy isn't? Lol. Since being with him I've become this overly jealous girlfriend. He has come to me about possibly doing a threesome, but with my jealousy being in the way I refuse to do it. I hate the idea of him even being in the same room as another woman. Petty right? Ugh. But for whatever reason, as of lately I've been wanting a girlfriend, like wtf? I toss between having a girlfriend for us to share and wanting a girlfriend for myself. I've shared my thoughts on us having a girlfriend together but not about me wanting one for myself. Idk if i wanna bring it up to him, but idk how much longer i can hold back. Idk what to do or how to go about it. But as of right now I just want a girlfriend for myself. I have no idea what to do or what to think or say, please help?!