Google constantly being hacked

[boyse7en]

I keep getting email form Google telling me my account has been hacked:

[i]Hi MY NAME,

We recently blocked a sign-in attempt to your Google Account [MY [e-mail]].

Sign in attempt details
Date & Time: Sunday, March 1, 12:00 PM GMT
Location: United Kingdom

If this wasn't you
Please review your Account Activity page at https://security.google.com/settings/security/acti... to see if anything looks suspicious. Whoever tried to sign in to your account knows your password; we recommend that you change it right away.

If this was you
You can switch to an app made by Google such as Gmail to access your account (recommended) or change your settings at https://www.google.com/settings/security/lesssecur... so that your account is no longer protected by modern security standards.

To learn more, see https://support.google.com/accounts/answer/6010255...

Sincerely,
The Google Accounts team[/i]

I've changed my password four times now, the last time to a 10-character random number and letter string, but it is still getting compromised.

Any ideas what is going on?