When I'm sent an iMessage, it doesn't say delivered on their device?

I have an iPod and an iPhone, when people send me iMessages it would come through on my iPhone. However, over the past one or two days when people have sent me messages to my iPhone it doesn't come up with the 'delivered' message under the message they've sent. I can send iMessages off my iPhone and they're delivered but people can't reply. Also I have my iPhone reachable by email so even if someone were to send an iMessage to my email it wouldn't come through on my iPod, but my iPhone, but now they're going to my iPod. I don't recall changing any settings so I have no idea what's triggered this. I turned them both off and back on again but nothing seems to be working.

Something must be up with your appleID or iPhone I would suggest going to the apple store or asking this question on the apple store online forum.