I look at him so different now

Me & My Boyfriend have been together for 6 months , & his birthday is coming up Dec. 31 && He Just Asked Was I gonna give him a Threesome for his birthday , my response was wtf really ! And it literally made me sick on the stomach after he asked && he was so serious ! I told Him that I look at him so different now ! Does anyone have any advice , what should I say or do ?