I don't know how to feel...

my boyfriend asked me to have a threesome with me, him, and my best friend. my best friend isn't into anything like that neither am I. He then asked for the three of us to go movies together and take a picture. He said he is going to post it on Facebook with the caption "my wife and girlfriend"! what do I say to that. I feel like I'll never be good enough for any man already. here I was thinking he's the one and he hits me with that. Like what do I do?