Then it appears there's obviously a larger issue that needs to be fixed. Do you have another computer, maybe borrow a laptop to test on your connection? Are you using a router?.. if so bypass that and plug directly into the DSL modem.

Also worthwhile to power the modem and router if you have one off, wait a minute or two then power on again.

Your ISP should be able to set up a 24 hour line test on your connection to see if there are any issues.