Some factors may hinder the observation of your cervical mucus. These include presence of sperm, arousal fluid, and lubricants used during intercourse. Like fertile cervical mucus, these substances are stretchy and moist, so it can be difficult to tell them apart. There are ways to distinguish fertile mucus from sperm (How to distinguish fertile mucus from sperm?) and arousal fluid (How can I distinguish fertile mucus from arousal fluid), but it's best to avoid checking the mucus shortly after intercourse altogether. Also, be careful with lubricants. They may not only distort your observations, but can also be harmful to sperm. If you suspect any factors are affecting the reliability of your cervical mucus observations, write it down in the "notes" tab in OvuFriend. This will help you track the cause of unusual mucus on a given day.