Message history?

The message history for all my messages in the message app on my iMac have suddenly disappeared? I don't have cloud sync for my messages, but I do have my account enabled for messages on my iMac, this has always allowed my iMac to send and receive text messages (the only difference not having cloud sync enabled is that if I delete messages on my iPhone, it doesn't delete on my iMac, which is why I disabled it cause I liked having my iMac always having a full history of everything).

But starting yesterday all my text messages on my iMac only show the single most recent text message for every contact. I double checked my preferences are to keep messages "forever" and "save history when conversations are closed," it doesn't appear I've had any system or app updates. Anyone have any clue what's happened?