My boyfriend is disgusting man I ever met

I can't believe that I loved him, he is literally red flag and I can't get over him. It started when things get spicy we did it and suddenly he brings up that he's fantasizing people watching us, I just ignore it since some people have that kink but then he bring up that he want my sister to watch us do it, and then told me that he wanna have threesome with her. I still can't believe everything that he said until now. I really wanna break up with him but it's so hard cause he's my first boyfriend and my first time...