Oral HELP

So me and my boyfriend have been together for a while now. I’m into BDSM and DDLG he knows I’m a little and that I like things a bit more kinky I guess you could say. I’ve been trying to get him to finger me and lick my clit but no matter what I do he just stops not even 2 seconds in. I’ve gone to the bathroom right before we did anything just to make sure I was 100% clean and ready(which I was) and he still stops and I think he’s gagged before. I’m always giving him blowjobs and I really want to know what it would feel like for his tongue to be on my clit. Any advice for what I should do or advice for him? He’s open to almost anything.