Hey there,
Sorry to hear you’re having trouble masturbating. One of the ost important things to remember about masturbation is that your mental state matters. This could mean being relaxed, taking your time, and having the privacy to do so.
In terms of masturbation itself, inserting your fingers is just one of many ways people masturbate. In fact, for some people, that method may not be pleasurable at all. I’m going to link an article that talks about other ways you can masturbate. Trying out some of these might help you to figure out what feels best for you.
https://www.scarleteen.com/article/bodi ... masturbate
If you still find that your hands are getting too tired, you could look into getting a sex toy such as a vibrator. Let me know what you think about the article!