If you want to see if your password has been used elsewhere(by you or someone else) you can enter it here:
https://haveibeenpwned.com/Passwords
WARNING!
Once you do this, that password is compromised. Not officially, he's not going to use it for nefarious stuff(probably), but you just entered it on a random internet form. Untrusted. So if you use this, make sure you change it after.