Delete your current Skype, create a new one and DO NOT let people you don't want ddosing you know what it is.
Get a VPN, the best I've found is HideMyAss, it's like $11 a month and a worthy investment if this happens often.
If your ISP has non-retarded tech support (only way you'll find out is by trying this), get them to block packets from the IP of the server that is DDoSing you. If they're using a dedi to ddos (very likely), this will stop it; if they have a botnet, this won't help. Ask to get an IP change - this will generally be done through your router settings and they'll guide you through it.
If you need any further help, PM me. Am happy to TeamViewer assist you in further protection against these assholes.