IMessage saying not delivered?

I'm texting my boyfriend from my iPod to his iPhone and it was working fine about an hour ago and when I went to send one just it had a red '!' And said "not delivered" however I'm also texting my friends iPhone and they are delivering to her? Does anyone know why this is happening?

There's a known bug with ios7 and iMessage. I rebooted my iphone and it fixed it. If not, you may have to rest your network settings.

I have an iPod too! It's because you have no source of Wi-Fi. That's why I always put my iPod in my house or my relative's houses when I need to text or FaceTime.

Hope this helps!

P.S. I just got some new headphones!