Relationship problem? Please help?

So, I've dated my bf for awhile, and he recently told me his brother just got a gf. His cousin is coming from Seattle to visit, and I don't know why I feel as though I'm in so much of a competition. I feel as though I want his cousin to like me better. I feel as though she's prettier than me and I have such low self esteem. Do you ever feel in competition with anyone at all? Is there any way to make me feel better? Thanks everyone. I feel really sad right now and I do act the way I do. Just a bit shy, but I'm not a faker or anything.