Actually, let's back up a bit here and start with WHY you don't tell your partner what you want in bed. I'll give you one guess (in rhymes with shmear).
Yep, you guessed it: fear. We're afraid.
And somehow we've made that fear our identity. "I can't ask for what I want because I wasn't raised that way." "I'm too scared", "what if he rejects me?"
Now listen, we could get real heavy into this subject because fear is pretty much the most common emotion we can feel, but I want to stop before I even get started because all it takes is a quick google search to find anything you want to know about the subject.
So let me just save you some time and get to a remedy: lean into the fear. You don't walk into the fire because you're not afraid, you want into the fire in SPITE of being afraid. That's the only place growth happens. When you let fear paralyze you and become your identity, you've let your STORY win... not who you actually are, but the STORY you've created about who you are.
So now that you know the skill, the only thing to get past is the fear.
You've got this.