Stress, in many forms, does effect your sex life. It could be work related, medical related, and/or kids related, just to mention a few! Medication or some other form of stress release (such as exercise) can curtail your stress related issues.
I have little external stress, but I do have clinical depression and that is a huge internal stressor that effects my sex life. Unfortunately, it's been worse since I re-started my medication.
It does...in that I have sex more often to release it! My partner and I have sex when we are stressed and it's a great way to make us both feel better. We need to get our rocks off and then go back to worrying about real things.