I get them all day, every day!
Anything religious in nature (i.e. the sight of a church, the mention of the Bible, etc) sparks a blasphemous thought in my mind automatically. Just reading your post caused me to have an instantaneous obsession, which of course, I will have to undo with my praying/crossing compulsion once I finish this...
It's especially aggravating for me because I am a very religious person, so it distresses me. I think what keeps me going is that I know that God knows I don't mean it, that He gave me the disorder to help educate others about it and to do research on it, and that religion is something sacred to me because obsessions only attack what you hold dearest. Good luck, God bless, and if you have any questions, feel free to ask me, someone who's been plagued with blasphemous obsessions on-and-off for six years!