Scalp - skin/not itchy

My scalp has never been dry or itched and my hair can get greasy really quickly if I continue to touch it. I try not to over wash my hair and will use dry shampoo or baby powder when it was greasy. Over the last month or so since I bought my new house I would wash my hair every 3 days to conserving water because my well was being worked on, which was fine because I don’t normally wash my hair every day anyway. I have noticed that if I scratch my head there will be white under my nails. I know that it is my skin, but I’m not sure why it is happening. My head does not itch at all but since I know that if I do scratch my head there will be something there so I constantly do it. It’s making my hair greasy really quickly. I don’t want to hurt my hair or my scalp. Is there anything I can do to moisturize my scalp maybe? Or is there maybe too much build up that my hair get greasy quickly? * I was using the baby powder a lot early on but I don’t use it as much/or at all any more so I don’t think the white under my nails is the baby powder. And if I have been using it I’m making sure I haven’t been putting a lot. *

I am willing to switch products or try new products. I will try anything. Thanks!!