Im 13 and a quarter and i weigh 139 pounds, am i overweight??

It depends on your height.
If you feel that you are overweight, you need to:
-Eat healthily
-Exercise moderately
Ask your parents, a counselor, or a physical education teacher at your school to help you plan a sensible diet/exercise routine. You should also consult your doctor. Your doctor should be telling you if you are overweight enough to cause alarm or health problems.
Many young girls feel that they are fat when they are indeed NOT fat. I suggest you google a BMI calculator and see if "the numbers" say you're overweight, just for starters.

Adding on to what Little said, you're 13, sweetie. I'm not that far ahead of you, but I can tell you that you're still growing. Gaining a little weight here and there is completely normal and when you get out of your teen years, you'll most likely fill out in the right places. Don't worry yourself or stress out about your weight right now. I think you're fine. ^_^