What Must I Do About Anxiety In My Toddler About Other Kids Mocking Him Along With Fits Of Anger And Breathlessness?

Hello I have a 5 year old boy who started kindergarten and comes home with note from his teacher he is acting out he is telling me that all the kids are laughing at him and they really aren t he comes home gets really mad tells me that I m yelling at him and laughing he can t control his anger and screams and makes himself short of breath should I bring him into urgent care could they help him