If someone already as got your IP hiding behind a VPN will not help you because all a VPN does is mask your real ip by routing it through their network. I don't see how a DDOS attack would only prevent you from going on TS when someone attacks you it brings your whole network to a stand still not just one program so maybe look in to a little more who knows what you could of messed up. Have you been playing with your router? a family member? as anyone there tried messing with port forwarding and blocked all incoming/outgoing traffic from common ports?
You can check your ports by going
HERE it will automatically put your IP in all you need to do is insert the ports you want to scan and seen as your having issues with TS the port would be
9987 if its open then you know to look somewhere else.
Check the TS error logs Its under something like Tools> Server Log
Here are some more TS ports you can check just for the bants but I don't see why you would be having issues with them.
Default voice port (UDP in): 9987
Default filetransfer port (TCP in): 30033
Default serverquery port (TCP in): 10011
Default tsdns port (TCP in): 41144
Default weblist port (UDP out): 2011-2110 (first available port in given range)
I really really don't think you're being DDOS because you wouldn't be online at all if they really was doing it.