Help. Insecure

I'm talking to someone, but I'm super insecure. I find him very attractive, but I'm always thinking he's checking out another girl instead of me. Today we spent the whole day together, but when he suggested to go to the mall, I didn't feel comfortable. I am so insecure that I didn't want to go to the mall because I didn't want him to see other pretty girls. Helpppp. I don't know how to cope with this.