iPhone 6 issues with messages

I've got an iPhone 6s that I've had for a little under a year. Recently, my phone started deleting messages and pictures for no apparent reason and just behaving really weird in general. Instead of showing the most recently sent/received message at the top when I open the messages app, the messages are completely out of order, not chronologically like usual. I have the iOS 10.0.2 update on my phone. Also, not sure if it's relevant but my snapchat app is also not working properly (crashes, doesn't load stories properly) and it started doing these things around the same time as the message issues arose. I have tried soft resetting a few times, but that doesn't seem to do anything at all. Any help on how to fix this would be greatly appreciated!