I'm having trouble uploading new versions to google play, i try to update say 4.0 to 4.1 and it says that version 4 already exists, it doesnt account for the .1
What you have to make sure is that you changed the VERSION CODE which is an integer number and that's what Google looks for to distinguish app versions.
The integer version number has no meaning other than the use from Google which detects a change in the version. That's why you have a "display-friendly" representation of the version which you can use to type anything.