I don't know how to act.

I've been feeling so down about my boyfriend lately. It's because he talks to this girl and she likes him and they talk all the time. He showed me they were sending snaps and he sent her a snap of his muscle with a caption responding to her snap idk they were talking about something. Even though I made it clear I don't like him talking to her he still does and sometimes I feel like he could be talking to her but neglects me. I just don't know how to act I feel very down and sad that I overthink. Am I being dramatic?