If you have used God's name in vain you are a Blasphemer
This is a very serious thing in the eyes of God
If you have taken the Holy name of God who gave you life and every other good gift and have brought it down to the level of a four letter filth word to express disgust.
If you have spoken of God, in such a manner that you do not give Him honour as your creator and the one who will judge you for every word, deed (action) and thought.
You have committed blasphemy. Consider what the Bible says about this...
"God will not hold him guiltless who takes the name of the Lord in vain." (Exodus 20:7)