The taste of his pre-cum seems to be making you even hornier, not to mention the feeling of his cock growing even bigger and harder inside your muzzle. "That's it, be a good bitch and get me nice and hard so that we can get to the main attraction" Duke says, gesturing to the wet pussy beneath your wagging tail.
Somewhere inside the back of your mind, your human side is trying desperately to break free of your canine instincts. "I'm a human and I guy" it screamed inside your head and you struggle to listen to that part of you, but the bitch in heat makes your legs shake, your pussy wet, and offers you untold pleasure. What are you going to do?