Have a look in chrome settings at what its set to use as start page
You could try disabling all your add ons and see if it goes away.
If you have a google logon, try reseting chrome as then you can get all your add ons back after its reset and it may fix this: http://www.howtogeek.com/171924/how-to-reset-your-web-browser-to-its-default-settings/
logon also includes all your bookmarks so you don't lose much resetting chrome