Oral sex help

Ok so my boyfriend has gone down on me twice, but has yet to get me all the way there. It was my first time going that far sexually but he isn’t a virgin so I figured he’d do just fine. The first time I really enjoyed myself even though I didn’t come and just chalked it up to it being his first time with me and figured we’d get it next time. Next time came, but I did not. Sometimes I start to get close and then I think he switches something up and I lose it. I’m kinda shy when we’re getting down and I can’t bring myself to say anything in the moment to tell him what I liked and didn’t like because I get too embarrassed. Then when he realizes he didn’t get me all the way there he gets really down on himself and feels really inadequate. How can I help him out? I don’t want to fake it because I feel like that would be detrimental in the long run but I’m nervous he’s not going to figure it out