Eew why does he want a 3some?

I think it's GROSS. I think sex should only be between 2 people who love each other. My bf brought it up 3 times, and the second time he decided he didn't want anyone touching me, so I was relieved. Then he brought it up again, and even sent me a pic of the guy who wanted to do it with us. First of all, im only 16 and my bf, whose 24, was my first and I don't wanna have sex with a stranger!! The other guy was like 21.. I told him off completely, and then he said he was joking and hasnt talked to me in 3 weeks. I'm not stupid, he was serious. I just feel like if he really doesn't mind watching some other gut go inside me, he doesn't give a f*ck about me. And that's what hurts the most :'( he even asked me to give the other guy head !!! Wtf! :(((