My ex makes me anxious

I have struggled with anxiety and panic attacks for years but recently I broke up with my boyfriend because he was cheating on me and now he keeps adding me to these random whatsapp groups with his friend and it makes me feel sick, what has he been saying about me? I don't want people to hear lies from him about me ;-; It makes my heart beat super fast and this ex has brought me so much pain im my past even a notification from him can give me a panic attack. I wish I never met him