There are lots of stories and research about sex and acne. Some say it helps, other say it makes it worse, most just end up saying more research is needed!
In the broadest sense no one doubts there's a relationship between sex hormones and the condition of your skin and hair. The main hormone culprit is testosterone - both women and men produce this.
Sex hormones, are produced all the time and not just when you have sex. A very tiny amount of extra testosterone is produced during sex. So whether sexual exercise per se will influences the levels of hormone enough to impact on acne, nobody really knows.
On the plus side regular sex can be a great way to exercise, build up confidence and get rid of stress, all of which can help with looking and feeling better about yourself.
Sorry there isn't anything more conclusive.