Some guys have absolutely no idea what they're doing down there. Your vagina may as well be a map to Middle Earth and even then, Sam and Frodo couldn't reach Mordor without the help of Gollum. Unfortunately, he's on his own and if it's the first time that you've been together, you're too polite to ask him what on earth he's doing. It's mesy, he's fast and vigorous and to be honest, completely winging it. Your G-spot may as well be Pandora's Box at this point; lost and unable to be opened. This is why it's important to work together because if you're in this situation and don't speak up, he's going to think that you're having the time of your life and it'll go past the point where you can comfront him about it.
