threesome

so i need inputs and thoughts on threesomes. i’ve never had one but my boyfriend has asked me about it. he even told me i could pick the girl but i don’t want him thinking he can go fuck her because i’m also really jealous as it is. like he can only fuck me in the threesome, does it make sense at all? like i also don’t want the girl thinking she can fuck or try to give my guy head. idk i need opinions on this.