I can't sleep because my ear itches! Could this be related to stress?

Unlikley. You can try some mineral oil in the ear before you sleep (assuming there is no hole in the ear drum). There is also a nice prescription medication for itchy ears called dermotic oil.. Your primary care could prescribe or your local ent.
Sleep. Stress could cause itching as a symptom, ear itching seems specific, rule out a bite sting etc before assuming its psychological.