How do i fix things?

Ive been in a relationship for 7 months already and theres problems happening now and im having trouble with confidence and communication, when he knows something is wrong he asks me whats wrong and i grt scared and give him a excuse that theres nothing wrong and then i end up telling him later on whats wrong and its gotten so bad that if i dont fix things my relationship could end how do i fix my communication and confidence?!!