Can't identify if I have dandruff or dry scalp

So basically I've been noticing some white stuff falling from my head when I run my hand through it backwards if I do it forwards then nothing happens I asked my mom to take a look at my hair and she said that it was clean and I had no flakes but no matter what I wash my hair with it keeps falling out even after a shower, I tried head and shoulders, head and shoulders + conditioner, only conditioner and now I'm trying no shampoo no conditioner. Can anyone help me identify what it is?