My boyfriend in contact with his ex :/

 my boyfriend and I i’ve been together for about nine months. His ex-girlfriend from I last year still won’t stop messaging him even though their relationship ended almost a year ago and he blocks her but she messages him on different social media platforms and makes fake accounts to talk to him it makes me feel sh*t when I’m with him and I see notifs from her. He sometimes replies to her and he actually reads the long long messages. The other day she unarchived insta photos of them together which was weird as f. How should I feel? What should I do???