Blasphemous thoughts

I need some advice. I'm going to be as short as possible. I struggle with intrusive blasphemous thoughts. They just appear in my mind whenever I'm stressed or anxious. I know that I would never say anything against God but sometimes they pop up in my head and I stress over them. I constantly overanalyze them, what if that's what I really think about God? I fear that a lot. I fear that I secretly agree with them. But then again, I keep on telling myself I could never agree with those thoughts. I feel like I lost touch with myself. I'm constantly under stress because of that. Please, but please tell me what to do. Are there any prayers dedicated to this problem? I even talked to the priest and he told me to stop paying attention to these thoughts. Please give me some advice.