I installed the wallet from Bitcoin's official website on 4 computers each running Microsoft Windows 7.
Moreover on each of the 4 PCs, I installed OpenVPN client, meaning each of the computers access the internet via VPN.
Suppose I do not use an online Bitcoin mixer to further anonymize my transactions.
Instead I transfer my Bitcoins from one computer to another, all the while making sure that the VPN gateway/exit node is located in a different country.
Question: can my transactions be traced back to me?