I would suggest that you contact the DSL provider and find out what level of service you can expect. There is very cheap DSL that provides a bare minimum of service and there is very good DSL that costs more.
It's quite possible that you have a service that only provides 500K-1MB down (much slower up). If that's the case only a service increase will help your problem.
If you do find that you have something like 2MBx5MB service but are seeing issues then you start some trouble-shooting. Do you have any kind of portable computer, tablet, smart phone? If so, you can get close to the router with that device, sign into the WiFi and see if you get the same terrible results or not.
