I am a teenager(13)
I am usuaully a very happy person and I smile lot and laugh a lot but then out of no were I think of something sad or something happens and I lose it. I cry for hours without stopping over nothing and I think that I am completely alone and I can't do anything anymore.

I calm down eventually but I have recently had one of these sad times almost everyday. I'm not depressed but what is it?

Well, maybe your stressed out. I know that I have those moments all the time. Its not bad to cry it out, but if it happens frequently then maybe there is something going on that you should talk to someone about. I recently got tested for depression and my test results showed I wasn't depressed either. Although I go to a psychiatrist every week and talk to her about things that are going on. Its nice to vent to someone. Maybe if you have a best friend who you can really trust and talk to about anything. Maybe if your in one of those moments call her up. I honestly would say crying is better then holding it in. Maybe your just having a stressful time. TALK TO SOMEONE YOU CAN TRUST, or at least vent to. It really helps!

It really could be anything from a chemical imbalance in your body, to stress, to some level of depression. ( people with depresson normally never know they are)