Hair Scalp feels dry & itchy!!

Ale • 22 & still young || Navy Wife ⚓️ || TTC my 🌈 👶🏻 w/ amazing husband 💍 ||
My Hair Feels Great Most Of The Time But It Is My Scalp That Itches A Lot. Most Of The Time. I Have 24 Inches In Length & VERY THICK. Lots Of Hair. I Stopped Dying My Hair Long Ago & All I Do Is Wash It Every 2-3 Days. It Gets Oily Yes But I Let Them Loose I Guess. My Hair Is Always Down & I Just Don't Know What To Do. Only Places I Put My Olive Oil Spray Is At The Ends; Never The Roots. Cuz I Know That Part Of My Hair Is Pretty Healthy. Besides All Of This I Get Itchy & Sometimes It'll Burn. 
I Tried My Hair Treatment Of Putting Castor Oil In My Hair & Massaging It At Night. But I Do That Like Once A Week. It's So Frustrating. My Mom Says Its Probably My Shampoo But I Don't Think It Is. I Ise Garnier I Think? Or The Herbal Essence Ones.
Anybody Have This Problem? What Do You Do? Shampoos? Any Thoughts?