I feel like my friends are leaving me out?

Okay so I feel like my friends leave me out/exclude me. it's really annoying. Like okay well they invite me to stuff like to parties and all buuuttttttt for example when we are sitting in choir we are all in the same row it goes like this: me (i'm on the end), *Mary, *Anne, and *Kathy (pretend names). And they'll scoot their chairs slightly towards each other and they'll talk and leave me out and yeah:/ what should I do?