Hi there teeny18, and welcome to Scarleteen!
Well first of all, I'm glad to hear that you haven't experienced anything traumatic that made you feel this way.
To dig into it a bit more - what kinds of thoughts come up for you before you go to masturbate or as those gross feelings come up? Are you thinking about your body, or what other people's bodies are like, or something else that you've seen or heard about bodies?
I'll also say that getting in touch with your body is a process that can take time. Obviously it can be hard for folks who have experienced trauma or difficult things, but it can also feel kinda strange/unpleasant if you haven't done it before. Learning how our bodies work and all the weird and wonderful quirks is part of having a body, and it's kind of a lifelong process because our bodies are always growing and changing. You might find giving The Sex Goddess Blues: Building Sexual Confidence and Busting Perfectionism
a read-through; even though some of it is about expectations around partnered sex, there's a lot of good stuff about the struggle of getting to know your body in there as well!