Broadband :: Century Link DSL Wireless Connection Much Slower Than Wired?

I have internet thru Century Link (DSL). I also have a Netgear N-300 wireless router. My computer is 4 years old and is an HP with a G wireless adapter buit-in. Until yesterday, my provided internet speed was up to 7mbps. I received the same speed regardless of whether my computer was plugged in directly to the modem (1), plugged directly into the router (2), or wirelessly. We just upgraded our internet to 40mbps. Now, I get the 40 mbps when my computer is plugged into the modem or router, but wirelessly I only get about 4 mbps, 1/10th of what I get with wired.