Hi Pips, and welcome to Scarleteen.
First off, I promise we will not judge you for reading fanfiction!! It's not like none of us here do that.
When you're trying to masturbate, are you doing it when you're already feeling aroused, like when you read fanfic you find arousing? Or are you trying to arouse yourself by masturbating when you aren't yet feeling turned on?
The reason I ask is that many people find that sexual touch doesn't feel good, or like much at all, if they aren't already aroused. So if you're not feeling arousal at all, touching yourself might not feel very exciting. It doesn't sound like you're doing anything wrong, but it's very very common for people to take some time and experimentation to find out what feels good and works best during masturbation.