Hi there, at 19 it's wonderful that you are noticing all this. Remember you can choose who you want to be. Stop yourself from reacting automatically to events. Appraise your behaviour and emotions. Your age and your insight are great prognostic factors.
Next Steps
Read about mindfulness, the power of now by Ekhart tolle is a good start.
Health Tips
When things are getting out of hand, don't delay help seeking. Find a therapist who can