Go to your email provider's website and log in to your email service there. (i.e. do NOT use an email client, such as Outlook, Outlook Express, Windows Live Mail or Thunderbird, and do NOT use an app on your phone or tablet).
If there's no mail visible there then, almost certainly, it's almost certainly because nobody has sent you any. (Take a look for a folder labelled 'spam', 'junk' or similar though, and check whether emails have been going into there; if they have use the option to mark mail as 'not junk' so that it doesn't happen again).
If there is mail shown on your provider's website then please post again and tell us which device isn't receiving your emails. (e.g. 'my emails aren't being forwarded to my Android phone; I'm using the default mail app'). Then we'll be in a better position to help you.