Why do girls always doubt guys?

I'm guessing that it's a guy that's asking this question.

Girls often doubt guys because guys aren't always as sweet or caring as some girls would want.

Lots of girls think that guys are going to act just like their best friend, but when they find that some don't, they tend do doubt you guys.

So as long as you respect that, girls maybe won't doubt you as much.

Hope this helps! : )