Gmail account is a month behind in all emails

My gmail account is a month behind in all emails on my iPad only also every time I go on to my email site on my iPad only a message comes up I need go to settings and renter my email logon but keeps telling me my pin is wrong am very frustrated this has been golng on for some time none of the help sites seem to be able to help hope you can help many thanks my email address is *********@gmail.com