Hey don't worry about it, unless you feel overweight or that you are slowing down.
I'm in college 156 6"2 and I run 100 miles a week, I was 151 in high school with less mileage, but now have faster PRs.
Sometimes it is just impossible to lose weight healthy.
If you want to lose weight because you think you could go faster then count your calories, boost your mileage, include light weight training or swimming, or just eat your vegetables.
Daniel Lincoln, one of my heros, is 151 and Broe is about the same, those dudes are freaking fast and they are pretty "heavy", we all can't be Lasse Viren at 6'2 and 131lbs.
Don't sweat it, keep running, good luck, and appreciate your last seasons of high school, you will get faster as you grow older, but everything else only gets harder. I know everyone says that. Good luck!