Am I the only guy who feels insecure about this situation?

Ok, so I've been talking to this girl for a little bit and I really like her! And she likes me! But everytime we go out or I introduce her to some of my friends I always think what if she likes someone else or looks at someone as like "there very attractive I want someone like that" or "his friend is really attractive I wish I was with his friend" . Idk what to do or how to feel it just seems like I could lose her at any second