Maybe .. Have you selected any options available to dissable IP Ver. 6 & the likes of DNS Leaks. What DNS are you using. Your ISPs or are you using something like Googles or your VPN Providers.
What about personal information available online about you. Do you have a FB account. How did you pay for your VPN Sub, Credit Card, Debit Card, or an Anonoymus Gift Card. Can the Payment be traced back too you.
What encryption are you using? Also what level are you running your VPN on on the OSI model. Are you running it on the 7th Application level or do you ave a VPN Router for something like OpenVPN.
What OS are you using? Windows. (Please don't say windows)
.. How strong are your passwords. Are you using any custom Kernals; if you are using a Linux OS.
And also, how often do you destroy the DATA on you terminal. Also is your HDD encrypted.
That above; is just the basics.