iMessage is suddenly not giving me "delivered" confirmation.

As of last night, iMessage on my phone is no longer giving me confirmation that my messages have been delivered. In the past, it has worked completely normally. After sending a message, I'd get the "delivered" confirmation under the blue text bubble. That notification is no longer showing up, but the people I'm texting have apparently been getting the messages. It's driving me nuts that they aren't showing that theyre delivered - which usually only happens when the phone I'm sending the message to is off, out of service range or something else. Strangely enough, the people who have read receipts on are still transmitting the "read" notification - I don't see the "delivered" notifification if they read the message it shows that it was read.

iI've done all typical troubleshooting techniques - soft reset, sync with iTunes, reset network settings, etc...nothing has worked. Please help! This problem is making me pull my hair out. Although it may seem like a nonsense issue, confirmation that my messages were delivered are critical in my line of work, which is one of the reasons I selected an iPhone for business purposes to begin with. Thanks a lot!