85 lbs is too light for someone who is 5'4". This means you are underweight and you should do something to add up the weight. This is because the ideal average weight for someone with your height should be 135 lbs. Check out http://www.healthchecksystems.com/heightweightchart.htm.
As long as you're not starving yourself, you shouldn't worry about your weight. Some people are built differently. I'm 13, and I weigh 80 pounds and eat a lot. I think you're pretty talented, and I'm sure if you practice more, you can get somewhere with it.