How do you know your friend isn't using you?
what can you do to find out?
A friend who is using you will only want to be with you when he/she is benefiting from what you are offering or from what you get when you are with your other friends. They will not be there when you need them the most and will disappear when you are trouble. Go to http://friendship.about.com/od/Types_of_Friendships/a/How-Do-You-Know-When-To-Call-Someone-A-Friend.htm for details.
well are you in a situation where you think you are being used but isnt sure?
They ask for favors more than to talk.
Ask a another friend to find out
You would know by the way you are treated