Can pinched nerve or strained muscles in neck/upper back cause tingling in both hands? Slept bad, pain for a month, headaches, tingling in both hands

strained muscle. Most likely you developed trigger points in either your neck or upper back muscles. You did not do it by sleepimg improperly unless you slept on your head. It is most likely from improper posture, slouching or not in proper shape/conditioning with muscular imbalances. If the tingling continues you need to see your primary care doctor, if you have one or a neurologist for an evaluation.
See a Spine . Specialist or spine surgeon. You may likely have a herniated disc, or cervical stenosis, which has to be properly diagnosed and effectively treated.