On my Jenkins I configured:
Source Code Management
Git repository: https://bitbucket.org/username/project.git
credentials: username/
As @Adrian mentioned, you still need to select "Poll SCM". It's a little unintuitive, but when the BitBucket webhook sends a request to Jenkins, Jenkins will poll for changes on all jobs that reference the BitBucket repo where the change was made. You can set a long time interval for the poll, e.g. @monthly, as you don't need Jenkins' scheduling to trigger polling; the web hook will take care of that as soon as a change is made.