If you are being used then someone is taking advantage of you and benefiting from this dishonesty in some way. It may be a relative who takes advantage of your compassion to have you do things for them, or a friend who only hangs out with you because you pay for everything all the time. Being used is not acceptable, and if you find out that someone is using you then the situation needs to be addressed immediately.
How could you forgive someone who backstabbed you. Well you really can't without the help of God. Our human nature is to egocentric to be able to forgive anyone, but God's Spirit can overcome any human weakness. And so you just have to ask God to help you forgive that person. And you ask God, until you forgive to the point that you even pray for that person. You are going to tell me, I don't want to think about that person who did wrong to me and pray for him. Well, in order to really find out if you have forgiven that person pray for him. If you can't then you have not forgiven him. You sill are holding a grudge..a human being can full himself many times. Just pray a few times you don't need to do it for the rest of your life, just enough to know if you have truly forgiven that person. Because many of us, including myself may think that we have forgiven someone, but in reality thinking about them still makes us feel angry, sad, frustrated, etc..But if you think about them and you feel love, peace and just a letting go feeling of frustration and anger toward that person, than you have truly forgiven that person. Why is it that important to forgive? Because you need to set yourself free from the pain that they have inflicted on you. Otherwise you will carry that pain and it will drag you down. When you let go, and let God be the judge and be the one that will take care of the wrong doing of people, than you feel free. You have crushed that evil spirit that doesn't want you to move on and focus on the right people in your life and the important things that you need to do to achieve your goals and dreams. Remember forgiving doesn't mean you approved what they did, and it doesn't mean that you choose to still be in their lives; it just means that you refuse to hold on to any negative emotions in your heart. You deserve to feel free and you deserve to feel happy and peaceful; forgiveness is an essential key to the road of peace, love and success.