Over thinking

On the 20th will be a month with my amazing boyfriend. It really hasn't been that long but I'm so scared still that I'm going to do something that scares him away and over thinking has been a major part. Before this I was in a relationship for 3.5 years that was my first everything so this relationship I'm comparing to the last on does and  don'ts. One thing that I'm trying so hard to do is not over think things and I need help with ways and things to do to help over come the over thinking.