Is my lover's new female friend better for him than me?

Hi, I'm 19 years old and I was hoping for some advice regarding feeling jealous. My partner and I have been together two and a half years now. He chats to a younger girl who shares similar interests as him and they talk quite a lot. Due to my own insecurities I can't help but feel that I'm not good enough or that he'd be better suited with her. I'd really appreciate some advice about how to get around this feeling and any suggestions on how to be more confident would be great. Thank you.