I think my son has anxiety

My son is 5 years old and for years now, I have noticed he is a lot like me when it comes to being social and involved with any activity. It never really occurred to me that it could all be a part of anxiety. I never knew it was an issue for myself up until 2 years ago when I started experiencing more symptoms of anxiety. For almost a week now, my son uses the bathroom before school and he doesn’t eat breakfast anymore. This is something I used to do. He also says his stomach hurts. If it’s the feeling i used to get, I now understand and wish I wasn’t so hard on him. Now I have to learn how I can help him overcome whatever is making him nervous about school. I never had to deal with this for a child. Any pointers would be appreciated? I try to be positive every morning and keep his mind off of actually going to school.