I am almost 12 in 3 months. i am around 144 lbs and i was a gymnast when i was little but quit in 2nd grade . and i was wondering if i was overweight?

Depends on height.: These days, to determine if someone is overweight we employ the BMI (body mass index), which granted does not take into account body composition. With your weight, you would be considered overweight if you are less than 5 feet 3 inches in height. That being said, you're young and have several more years to grow taller, so I wouldn't necessarily worry too much about it yet.