You couldn't be bobbing your head up and down any more right now, and HE STILL HASN'T COME. In the time you've been going down on him, you've made a mental shopping list for groceries, composed an email to your estate agent to ask for a new washing machine, decided on what presents you want for your birthday, and considered how you're going to get your S.O to make you orgasm once this is over. And he still hasn't come. Thinking about it, he probably hasn't orgasmed yet because most of your attention has been focused on everything except giving him the best time ever. You're a terrible person. It's concentration time.