Insecure

I feel like I am constantly so insecure because the guy I am dating is always having girls blow up his phone or message him or snapchat him and even after him telling them we are getting serious they still continue to do so and it makes me feel so insecure and in constantly wondering if he talks to them when I'm not around I wish I didn't feel like this ugh can anyone give me any advice on how to not feel this way? I've been in pretty toxic relationships so I feel like that's why I don't have very much trust in people 🙄😩😩😩😩