If you are just starting out, where did you get your router, was it supplied by your ISP, or, id you buy it elsewhere. If so, it may not be compatiblwith your provider...Do you have filters installed on  EVERY device that is connected to the phone line? That is absolutely necessary. These filters are not totally  reliable, they too die a silent death occasionally, and will take your connection with them...

By all means, check with your provider to be sure your line has a good DSL connection. They can do that from their office, and give you an instant answer aas to the quality, or death of your line....