Friend problem can you help?

I am friends with every girl in the cl (all 6 of them) and they are in their own groups. E k and M. then there is hk sk and s. I hang with e k and m a lot, and rarely talk to sk s, and tlak some with hk. If I hang out with sk hk and s i always feel left out from e and them. But when i hang with e and them i feel bad for my other friends. I am ALWAYS put in a different group for e and them. e k and m are ALWAYS together somehow. they are grouped up together, and are usually called out, all 3 to help out with special things. The principal even knows i hang out with them, and yet im always separated and left out frmo them. I cannot sleepover or go out as much/or as late as them. So you see i feel left out, and mad at them but yet i love hanging out with them. with hk and them i like hanging out but if i see M laughing really hard with e and k, i want to join them instead..:/ HELP ME!