I agree with thinkpads_user.
However you can check your line with
http://www.dslreports.com/linequality.(its free to join and use). Based on the results, you can point the technicians in the right direction from your end isolating it. (It might be network congestion in the area which will cause the symptoms your having.)
More in likely, hardware on the ISP side is startin to go bad and they having figure out which piece yet or not enough customers complained.
Regards