Agree. I had this problem.
I called it "cum shy". I was open about it and just accepted it.
Over time I got over it and can cum with others no problem...
Just take advantage of it and tease your self and who ever you are with for long sessions
Love your phrase,
cum shy haha. Because it captures what happens to me too!
I think - as what many have touched upon - is relaxing and being in the moment with your guy.
I think having a strong bond or connection and knowing that there isn't any pressure to cum (or how to cum or where to cum helps in that regards). Just being able to be cool with your guy, and you'll relax a bit - and if it happens great; if it doesn't, you still shared an intimate connecting moment with your guy all the same.
For me, I think my '
cum shyness' developed from sexing women primarily before guys. With women: there's (a) flirting, then (b) foreplay, then actual (c) sex; so, learning to have sustainability throughout is a necessary skill. You can't explode too early because she won't be able to enjoy - depending on your refractory period.
So learning how to stay hard and view sex where your woman is able to reach climax was the primary and biggest concern. I think that contrasts with being with a guy. Guys are cool if you cum early or late.
Maybe spend more time just flirting/foreplay without the sex and see if that helps any. Remember every body is wired differently, so you may have to take a bit more time to find out each other's erogenous zones and how to build the passion from there.