Honestly, whether you're Charlie or not, Getting it on with Doomguy would be a... unique experience.
No, I don't think he goes full comic mode, but from what we've heard from both Carmack and the new 2016 lore, we have a pretty solid understanding that Doomguy's no nympho. He's a virgin at worst and super inexperienced at best. That sounds like a setup for some super vulnerable, dorky sub, but you have to remember what kind of man Doomguy is outside of the bedroom. He has been in hell killing demons for presumably thousands of years. It's his primary mission in life. Once you've reached the point where he can stop (i.e. when IT IS DONE), you've got the mammoth task of trying to acclimate Doomguy to normal life, to say nothing of sexual activity. He'd only strip after you've stripped, and from then on, you'll need to practically hold his hand until he knows what he's doing. Guide his hands so he knows it's okay to touch you there. Explore him to help him find what makes him feel good and where. Coach him with how he can please you. Help him get a feel for the rhythm of the act. Once you've been at it for long enough, his instinct will finally emerge from under his ingrained need for combat or vigilance, and you can be pretty confident that he can take it from there. He'll be rough, but very passionate and affectionate. If you've managed to get this far with him, chances are he cares about you. A LOT. He will unleash his inner beast on you, but he'll do so while holding you, kissing your neck, embracing you to where you're doing none of the work at all. The thought of hurting you would horrify him, so you would need to make sure to let him know he needs to slow down. After it's done, he'll hold onto you for hours, not letting go until you're fast asleep.>tl;dr: He's a tough nut to crack, but once he's open, he'll love you with all his big, ferocious heart