Hey, your best solution does cost money, but it is totally worth it! I've had a similar predicament before.
I just got a $30 powerline kit, which basically uses your house's electrical wiring to carry an ethernet connection, just as if you are connected right to the modem.
I use this one that I got from Amazon:
http://www.amazon.com/gp/product/B00AWR ... UTF8&psc=1It is very fast and I never lag or lose connection. Just plug one in down by your modem into the wall, then use the provided ethernet cord to plug it in to your modem, then do the same except for your computer!
Hope it helps!
