If you think your credentials have been compromised, the first step is to reset your password. Depending on the service, you may also need to reset your username or security questions. Additionally, you may want to set up two-factor authentication to ensure that your account is more secure. To do this, you'll need to register your phone number or email address with the service, and they will send a code to you each time you log in.
If you are still having trouble, you may want to contact the customer service team of the service you are using. They should be able to help you reset your credentials and answer any other questions you may have.