I took Plan B on june 2, three hours after intercourse and my period was due june 25. I am now late 19 days. Is that normal?

It may be BUT. Plan B works by hormonally interfering with fertilization of an egg. It is also possible that this type of emergency birth control prevents implantation of a fertilized egg in the uterus by altering its lining, and periods can become irregular, especially after its use. However, check a pregnancy test too. Best wishes.
Pregnancy Test. Plan B is only 50% effective at preventing pregnancy. While it is well known that Plan B can change your menstrual cycle, you must first do a pregnancy test to see if you are indeed pregnant or not.