Can you test your speed here and share the result? : http://speedtest.net/If there is something weird , your computer probably infected by a virus.
Your local internet provider may be the cause. Try to talk with them whether there is a problem or not.
You don't need fast net to play DotA but your ping sux. Try pingtest.net and post result
http://pingtest.net/help.php#q6Try to fix it and run the test again. If you loose too much packets, well thats problem. Anyway, as filibis said, contact your provider for help.
Download NetLimiter. See what is using your net.I had virus using up my upload which made in return my ping really high. I fixed it with formating all hard drives and reinstalling windows, but after some time same shit started happening again so i used net limiter and saw what was using my upload and put limit on it, since than i had no problems.