Insanely low speeds on Wifi.

My computer was averaging 70-75 mbps on wifi until recently, now I am lucky to be getting 5-10.

Its not my computer, as logged in to my friends wifi with it and got the same speed. As soon as I got home, back to 10-15. computer has not moved positions in the house, just all of a sudden a drop in speed.

Plugged in to the modem (not feasible to stretch a cable from my living room to office, so that won't help) i'm still getting my 100mbps, its only wifi thats an issue.