I have a painful shoulder especially raising my arm overhead from squats and overhead pressing. could it be a rotator cuff tear if i am only 19?

Maybe.: You would have more shoulder pain with your arm above the horizontal if it's a rotator cuff tear. Give your shoulder a rest for awhile. If you have more trouble with overhead, military-press-style weight-lifting, this could also be a labral tear that just needs some physical therapy range of motion, strengthening, and stretching exercises.

Possible: It's possible to sustain a rotator cuff tear at your age, but tendonitis from repetitive stressful activity may be more likely. I would avoid straining that shoulder for a week or so. you could also reduce inflammation by taking anti-inflammatory medication like Advil or Aleve for several days. If symptoms don't resolve, consult an orthopedic specialist for evaluation,advice and treatment.

Yes: Yes, it could. There are other possibilities including a tear of your labrum or issue with your Ac joint. Don't hesitate to be seen for a detailed examination and possibly further workup for a specific diagnosis.