My Bf wants me to have a threesome??

Before I got with my current boyfriend I was with a female and we sorta met by my nudes with her getting leaked. His friend had the pictures on his phone and saw them so he got mad at his friend for having pictures of someone without their permission. He found my Snapchat and we sorta started off from there, my ex gf was extremely manipulative and she’d send stuff to her friends whenever I messed up and my bf helped me leave her then we got together. We’ve been dating for over year and he told me he thinks it’s really hot when I get with another female and he wants to see me do it but I said no because to me that would be saying it’s okay for him to look at other women that aren’t internet females but is that really what it means? He said he’s not bored of our sex life he just thought it be really enjoyable seeing a different side of me. Could anyone really have a healthy threesome? Is that actually a thing? Is my boyfriend actually trying to cheat?