Come on guys, I'd get really paranoid if this happened to me!
When guys go through a lot of stress at work, they don't exactly feel sexy. You'll make yourself look better if instead of nagging him about it (I know you're not 'nagging' as such), you'll just be content with a kiss and cuddle for a while, that way he'll feel confident that you love him for him and not for his willy and he doesn't need to be a stallion constantly in order to seem attractive to you.
Try talking to him about work, what's worrying him, try to come up with solutions to problems or just make soothing noises or bitch about the people he doesn't like with him.