I seriously need advice.

I have a best friend (A), and she tells me we are best friends. Well, shes been spending a lot of time with (P) lately, and I don't think P likes me very much. I find myself getting a little upset when they hangout, and I think I'm jealous. I mean I am so happy that A has other friends, and I love that they get along together, but I keep catching myself growing upset that they hangout so much. Is that normal? Is there something wrong with me?