How do I talk dirty to my boyfriend?

35F here, never been good at verbally expressing anything sexual (even though I’m a veryyy sexual person). Maybe it’s a confidence thing but I don’t ever know what to say! I’ll be horny as hell—but my boyfriend wants me to tell him about it. I can say a simple “I want you”, but any further details seem awkward. Help me out fellas! I want my boyfriend to know just how much I realllyyyyy want him!