NAT Type Randomly Alternating Between Open And Strict?

So I use wireless internet because I don't have access to a phone jack in this room; therefore I can't use a ethernet connection.This is entirely random in nature and doesn't seem to be affected by anything I do (Disabling/Enabling firewall, forwarding the appropriate ports, creating a firewall exception and restarting modem/computer. It will be OPEN during a game, and then my wireless connection icon (signal bars) on the task tray will show a little yellow caution sign and then it will disconnect from the network, forcing me to open the list of available networks and reconnect. After this happens, my NAT will change to strict, and thus far I haven't been able to make it OPEN again. I'm at my wits ends here, nothing I do seems to have any effect at all on my NAT type.