What is this? Nipple discharge for years!?

So I’ve always had nipple discharge( since I was about 15, I am 20 now). Everyone’s first thing is “am I pregnant”.. no I am not lol. It’s been like this for years. I want to know, what is this discharge/ why have I had this? It’s more white when it comes out( it never “drips” though, and then it dries yellow? It’s also not crusty but not soft either?

So sorry for the weird pics lol I had to zoom in a lot so my hands look all weird.

Thank you to anyone that responds :)