What could cause epididymitis when the results of std and uti came back clear? can to much sitting and laying in bed do so and no exercise?

Sometimes no known cause. Occasionally allergic drug reactions. Lack of exercise or body position are not causes. Keep working with your doctor, ideally a urologist. Also discuss whether the diagnosis of epidymitis is certain, or if something else may be causing testicular or pelvic pain, such as the chronic pelvic pain syndrome (CPPS). Google for more info; the Wikipedia article is good.

Epididymitis is often diagnosed erroneously when there is testicular area pain/ discomfort due to other reasons like an epidydimal. cyst. Sitting and laying in bed will definitely not cause it. Wear a support underwear, use local heat. If not better see a Urologist