My boyfriend seldom cums from head? Is it him or me??

Every time I have ever given a guy head, I was able to make him cum. I have never had a problem with this before, and have received many compliments on my blowjobs. Ive always been consistent in achieving the goal. My current boyfriend and I have been together for nearly 8 months and this is the first time I've ever been with someone that I haven't been able to make cum from head with ease. He is 14 years older than me and cums no problem from penis in vagina sex. I have made him cum from head a couple times before. I've even made him cum from head while he had whiskey dick (hard and tedious but I did it nonetheless). My problem is that I get lucky whenever I make him cum because most times it's difficult. He does not cum from head easily and I'm starting to feel a little insecure. I know I shouldn't, but my boyfriend gives the best head ive ever received in my life (I orgasm 1-2x EVERY SINGLE TIME.) and I would like to return the favor. He is fantastic and I want him to be able to feel the amazing sensation I feel whenever he makes me cum every single time. I don't know what to do. I plan on talking about it with him but does anyone have an explanation for this? What are some new techniques I should try to get him more excited? How can I get him to relax and let his body succumb to the sensation enough to orgasm?