People like to say that your gut is always right, that "when there is doubt there is no doubt" but is that always true?

We are all humans and often insecurities can get the best of us, our minds can make up shit that isn't really happening and we often end up believing it because we get insecure.

It happens to me that I feel like I can't trust anyone. My "gut" tells me that people can be so good at lying that not even the best detective in the world can call it bullshit, so I tend to distrust everyone and everything someone says or does. And even when people sound convincing, my "gut" still tells me they are lying.

Knowing that our insecurities can make us believe shit that isn't really happening, is the gut always trustworthy?