Why is my macs download speed ridiculously slow?

i'v had my macbook pro for about a month now, and a few days ago my download speed went from an average of around 800kb/s to roughly 4kb/s. No matter which internet network i use at my school or which programm i try and download with the result is the same. The problem is localized to my computer as well as none of my friends are having an problems with their internet speeds. What the hells going on?