When you access your email (on an Exchange Server) through Internet Explorer, that means you are able to login to OWA (Outlook Web Access). Since you are able to login and see all of your information, that means the issue is local to your mail client/pst file.

You can remove the profile from Outlook completely, and set it back up. You won't lose any information since all of your info is stored on the Exchange Server. Once you set the profile back up and connect it to the Exchange Server, you will get all of your email/info back in Outlook.