Anxiety issues and school :(

Today was my first day of school and I walked past my ex-boyfriend so many times and every time I do I get bad anxiety he from it. How can I stop getting anxiety from him?? He broke up with me and I still have feelings but I'm trying so hard to get over him I just can't !! And today I felt so lonely and sad bc I barely knew anyone and my anxiety kills me to speak to new people I sit alone at lunch because of it !! Anyone know what can help me? I'm desperate 😞