Randomly feel like screaming and crying?

OK, I'm like 13 so don't think of me weird please! But sometimes when I go through facebook, look at these things i just want to scream and sometimes just cry! Okay, I can't be depressed because at school I'm like so cheery and hyper its just crazy. Could this just be hormones? I don't have my period at the moment but I might be due soon. Soo if this doesn't make sense I think I should just find a way to release stress, doing exercises seems to help me and make me feel happy. This question just feels strange to ask now, but I find it strange that I'm crazy like this, so help if very appreciated, thank you awesome yahoo people!!!!