Threesome

So this guy I am talking to really want to have a threesome with me. I’m really uncomfortable with it because we are not in a committed relationship. He never said we are in a relationship. He always say he is working on him. And not thinking about that. I guess he feels that he needs to have one with me since I had one. But when I told him that the one time I had one was because of my ex it was unexpected from the girl. I was really intoxicated and I did not do anything with the other girl. She did everything. And my ex just fucked both of us. I was not expecting that. He just thinks that I’m going to be down. I’m so confused what should I do? He wants be to do things to the girl but I’m not comfortable doing that. I told him I dont go both ways. And I’m not curious. What should I do? Should I stop talking to him. He keeps bringing it up that he wants one. But we are not in a relationship. We have not been out on a date so I just feel confused. I just feel used. Someone help. I am only into men and I don’t think of women that way.