Is my email account getting hacked?

So, this has happened two or three times now. I go to log into my email in the morning, and it says my password is incorrect. I change my password on a regular basis, and I have never given my password to anyone. Nor is the password easy. Even my best friend or my boyfriend would not be able to guess it.
When I get into my email, finally, there is nothing different. No deleted emails, no open emails that shouldnt be… nothing has changed.
What should I do?