These thoughts are due to ocd. These thoughts tend to drive us crazy because we react to them and then we tend to dwell on them. In the end we may end up fighting them to get rid of them. Fighting the thoughts will only make us distraught.
The thing to do is just notice when this thought enters your head. Don't give it any importance, shrug your shoulders and let it go. This may take some practice. Don't be discouraged. Logically, we know it is impossible to breathe in evil. Yet the ocd does something to our thought patterns or reasoning, where we become immersed in these thoughts, causing much anxiety.
Now, how is your diet. You must make sure to eat three balanced meals and cut out all sugars. Do not drink any sodas, not even diet. diet sodas are worse than regular ones, as they contain aspartame. No fast foods.