Why does my iPhone 5 stop sending messages?

It worked for a few days and then last night it stopped sending and receiving texts. But I could still make calls. Then this morning it started working again. But now it is doing it again and it won't send texts. The iMessages won't go through either. I'm horrible with technology so I really don't know what to do. I tried turning it off but it didn't work. And If I do a network or hard reset, then will I lose everything on it?

Added (1). It is a Sprint iPhone if it matters.

Sometimes the apple messaging service or iMessage is down and won't go through. I had this happen several times on my 4s, hasn't happened yet on the iPhone 5 though. It was a pretty big pain, but maybe if you are at home and having an issue while trying to use Wi-Fi, toggle off Wi-Fi and try sending the message through 3g or 4g. That also happened to me as well, my router can only use 10 devices at once, and I have about 20 linked over Wi-Fi. After it fills up it starts not accepting devices and it may say you are using Wi-Fi on your phone but you actually can't get internet at all to work. I would suggest trying to turn off Wi-Fi on your phone and see if it sends through the cellular network, if so you might want to reset your router or make sure your firewall isn't blocking the device.