problem with authentication in Sourcetree

Hello,
I have a problem with authentication my account in Sourcetree but I can log to Bitbucket. Firstly, I had a problem during pulling or pushing. Then, I decided to reinstall Sourcetree on my computer but it didn’t help. When I clone repository and try to log, the message shows up:
_Error: fatal: HttpRequestException encountered.
remote: Invalid username or password
fatal: Authentication failed for 'https://onowicka@bitbucket.org/gomezsap/gomezsap.git/'_

Could you give me some tip how to resolve this issue?
thanks!