So I'm pretty, so why am I so insecure everytime I hear somebody say some other girl is pretty I get?

Completely jealous and feel like I have to compete, not actually compete just feel. I mean even when a guy Im not interested in or my sisters or anybody say anything about somebody being pretty or gorgeous I starting feel so insecure with myself. Why am I like this i sware i hate i dont want to care. Please help me out?