Getting busy with your guy is an excellent idea—and not just because it’s fun (although that’s a pretty good reason too). Being sexually active also helps beef up your immunity, fight stress, reduce pain, and strengthen your relationship. But if you’re like two-thirds of women, you’re taking advantage of this health and happiness boost only once a week at most, according to a survey commissioned by the nonprofit organization HealthyWomen. The question is, why aren’t you getting more action? We asked experts about the excuses they hear most often—and what you can do to heat things up between the sheets.