Now that we have narrowed down the access attempt to Google spider, I don't think there is much reason to panic.
Nobody is going to login into your account and steal your Bitcoins.
The only worry you should have is where the spider got the link to your username.
The best you could do now is create a new account on Blockchain and transfer funds from old wallet to new one.
If the funds are very large, I would suggest moving most of it to cold wallet and keeping only a small amount on Blockchain.
Seems i found solution to my problem too.
Though i never ever posted my identifier or link anywhere .
But well! idk, it happened the same day when i tried to authorize it from my new laptop.
I think first i tried from my laptop , it wasn't working so i did it from my mobile, maybe that's why ?