Unless he’s been in a car accident and is hospitalized, the reason he’s not responding is less important than the fact that he’s not responding. This may have been a one time goal for him and now that he’s had sex with you, he’s not interested any more. That’s part of the problem with the term friends with benefits — usually, you’re not really friends. This isn’t how a friend acts. 😳 Sometimes people use the label FWB because they don’t want to relegate the relationship to hook up partners, but that might be just what this was: a one time hook up.
As for contacting him, don’t. If he wants to see you, he will. Since he hasn’t contacted you in over a week, he doesn’t. Time to move on and figure out what you’ve learned from this relationship and take those valuable lessons with you into the next one. 😉
I hope that helps!