What's going on with my Facebook IMs and my iPhone?

I have the iPhone 4 and everytime someone Facebook chats me it gets sent to me as a inbox. I am missing chats because it is not sending me an alert that I got one but instead just vibrating once. How can I get everything back to normal, get a alert when I get a chat or have it sent to my actual chat page instead of inbox? UGH! So simple, yet so annoying!