Email app suddenly is not working right - last emails I see are from august last year

[Leillia]

Suddenly, my email app isn't syncing properly. The sent folder has NOTHING in it and my inbox only has emails up until August 2014. I don't know how to fix this or why it is acting funny!!! But I would really, really like to be able to read my emails on my phone. (It's the email app that came with the phone... it has worked fine up until this second)