Anxiety in new relationship

A few weeks ago, a girl asked me out and I said yes and every day I get a really bad feeling and pressure in my chest. After she asked me out there was a point where she told me she liked someone else and after telling how I felt she said she would stay with me and she was just afraid of being hurt again.

Anyways, at one point a few weeks ago she sent me a screenshot of a conversation between her ex and her and the ex was telling her how it seemed her being on her phone was more important than them spending time together and I can see where he's coming from.

She is constantly calling people out of nowhere and wanting to hang out with her friends, I'm trying and wanting to trust her but every time she picks up the phone or makes these plans it triggers my anxiety and I've told her about how I felt and she said she's honest with me.

What has any of you done to deal with anxiety like this? I haven't been in a relationship for almost a year so I don't know exactly what is causing this...