When i download stuff, the internet connection is lost and then reappears for a few secs... PLEASE HELP!!?

ok, so i start a download, example: a steam game. my internet connection works just fine but as soon as i start a download, my bit-rate drops down to 0kb/s and everything else using the internet stops working including web browser. it stays like that for about a minute and then the bit-rate goes back to normal 1.6mb/s on my steam game download, but only for about a minute, which is extremely annoying! has anyone had the same problem? any help is appreciated!