The thoughts don't interfere w/ my daily life... much. Like, I'll just think about it while I'm in the bathroom. I'm not as worried as I used to be now that I have a cover over the toothbrush. The thoughts occasionally come up, not every single day, it doesn't consume me. If I didn't wash the toothbrush before using it, I'd think that the smell would stay on it & get in my mouth w/ germs & bacteria. Hence, the reason why I now close the lid on the toilet seat. Flushing, is how the smell gets on it.
Everybody has thoughts...the key is whether you can let them go or not and whether they interfere with your daily life. If you feel like these thoughts are interfering with your daily life, then it is a problem and it is time to see a psychologist.
How long have you been having these thoughts? Are they happening more often? Are you not able to get a handle on it when it happens? What do you think will happen if you don't wash your toothbrush before using it?