Just need to get it out.

My boyfriend and I have been together for almost 9 months and for the most part with side kinks occasionally.. our sex is vanilla. Which is great! It doesn’t bother me.. but he asked for a threesome about a month ago and then felt awful immediately after asking and hasn’t brought it up since. I don’t really want a threesome because it can come with some really big problems. Everything is fine I think.. it’s just if he wants to try something different I’ve always said we could. I try to get us to do stuff all the time and he says no. We literally really only do doggie and give him tons of head.

What can I do to make it more fun and flirty for him and get him to be more intimate with me?