the only way to know for absolutely certain is to look at the management interface for your modem, and see what it reports as the external WAN IP address. If you don't have access there, then you won't know for sure if the remote IP address you see is your own or a proxy.
You can try doing an nslookup on the IP address and see if it 'looks' like a proxyserver name or just a random user, but it'll be guesswork at that point.
You can try doing an nslookup on the IP address and see if it 'looks' like a proxyserver name or just a random user, but it'll be guesswork at that point.