I agree.
Stop saying you have a boyfriend. It means, "I'd be interested, except..."
Start standing up for yourself. Say "I'm not interested." It means, "I'm not interested, now or ever."
Save "I have a boyfriend" for those moments when you're a terrible person and you really mean you'd be interested, except you can't. (This last sentence directed at me, especially re: use of phrase "terrible person," so please don't whiplash me over this. I know when I'm a terrible person. (It is possibly frequently.) I'm not calling you terrible. Chill.)