My boyfriend won't go down on me

I always give him blow jobs and have asked him a few times to go down on me. He says he will do it but still hasn't, I find it really embarrassing asking him to and then him not doing it when he says he will. I get really excited because i think he's going to do it then he doesn't. I understand I can't force him to do it but what do I do because everytime i try to have a real conversation about him not doing it he says he will. Then again, doesn't.