iMessages from one contact is appearing under another contact, while the first contacts conversation has completely disappeared. When they send me an iMessage it will show up that I have an unread message, but I can't see it and it never disappears

This is pretty complicated to explain.

iMessages from one contact appeared under another contact. To make this a simple as possible, Contact 1 into Contact 2. So, when I go to text Contact 2, every message from Contact 1 shows up on the screen aside from some missing texts for some odd reason. I can't message Contact 2 either, they say they're sending but they never do send. When Contact 2 messages me, they show up under the messages app and in notifications, but I can only see the preview of the message and when i go into the actual message, it disappears and shows all the messages from Contact 1 again. Also, when I go back to messages screen from there, it shows the blue dot saying I have a new message, and that never goes away no matter how many times i go into that message to view it. All of contact 2's messages have vanished completely. I have an iPhone 5 and its up to date, iMessage is working properly aside from these two contacts.

I think it might be important if I mention that I also have a macbook pro, and everything is working fine on that. I can view my messages, send and receive messages from Contact 2.