Persisting Itchy Scalp, No Help With Natural Shampoos, Oils. Can It Be Due To Stress?

Scalp is itchy most of the time, tried over the counter shampoos and one from doctors prescription also natural shampoos and oils for scalp but it seems to loosen underneath the scalp, I have picked at scabs on the scalp and scratched it raw in many places trying to smooth the scalp of scabs, not normal dandruff... has persisted over a year and a half... lost my job a year ago, so I suspect stress is a contributer, I also fish from the ocean shore and pier where I have suspected picking up something from sand fleas or ocean birds which sit on the handrails that I have had contact with.