I've been through this myself, except you're experience doesn't sound as severe. My experience was due to the fact that I had finally felt unconditional love and I wanted HIM that way, and I wont bore you with the details, but either way it is a sin, it's blasphemy, and were all punished 7fold for every sin, that's why God cursed Adam and Eve like he did when he kicked them out of the Garden. Are you born again (receiving the new birth by accepting Christ into your heart)? If so, then don't worry, you're ALREADY forgiven. We ALL sin from birth to death, and sinning doesn't hinder being forgiven, otherwise no one would be forgiven. Remember JESUS paid it ALL when he died, he died for EVERY sin, except denying him into our hearts. So, my advice would be to pray to him, ask him to help you, ask him to remove these feelings and thoughts, and ask him to lead you to a righteous life. I hope this helped you out dear person, and may Jesus bless you for opening up and admitting this.
other source: personal experience