My baby is 3 weeks old she always has episodes of crying during breast feeding that interfer it also during sleep she never sleep quite, she always nervous, I do not know what I can do?

Check with your Peds. I would advise you to pay a visit to your pediatrician and have her evaluated. If everything alright, check with lactation nurse to be sure if she is latching right, and she left hungry or she might have just colics. Have your baby ever had a history of neonatal abstinence?
See below. She should be evaluated by her doctor. She may have reflux or milk protein intolerance.