Hi joplin.baby,
Actually, length of fingers doesn't really matter when it comes to fingering, because the most sensitive parts of the vagina and vaginal canal are up towards the front of it. The back 2/3rds don't have that many nerve endings, comparatively. When you try fingering, are you focusing mostly on trying to stimulate the inside? Or are you also paying attention to external things like your clitoris?
Too, it can help to remember that while fingering may feel great to some people, it may be underwhelming for others, or not really be the thing they enjoy most during masturbation or sex. How our bodies experience pleasure varies widely from person to person, so what feels amazing to one may feel "meh" to another. You can read all about why that is here:
With Pleasure: A View of Whole Sexual Anatomy for Every Body. So if fingering is starting to be more frustrating than pleasurable, there's no reason you can't switch your focus to other things during masturbation.