You shouldn't be embarrassed to talk dirty with your partner. He's someone that you should feel comfortable around. Besides, dirty talk isn't as complicated as it sounds. All you really have to do is vocalize your thoughts. If you're not sure how, here are a few words that'll amp up the dirty talk:
It's important to give him positive reinforcement, so that he continues to do the things that turn you on. Tell him that you love the way he touches your chest, kisses your neck, and plays with your hair.