After you get that, and you press POWER+VOL UP do you get into CWM?
Did you flash CWM (or TWRP) with Flashify or FreeGee or some similar tool?
It actually sounds like CWM/TWRP are not installed, I would flash again and then use the command "adb reboot recovery" to force the phone to boot into recovery, if you still get Mike on his back with an open chest plate, you do not have CWM recovery installed.
Remember, when modifying your phone there are several pieces to it, they all need to be done in order for this to work. Rooting is just one step, in this device that opens the door to allow another app to install custom recovery, and from there you can install ROMs.
You will not receive "official" OTAs when on CM, but some aftermarket ROMs do have an OTA system for their own distributions.
Don't confuse the operating system and the firmware. If you phone currently has JellyBean, there is absolutely nothing stopping you from running a KitKat ROM right now, I am doing it myself and it works perfectly. If you want to update to the "official" KitKat release at a later date, you may need to be prepared to restore your phone to factory defaults via LG's Flash tool and a KDZ/TOT ROM image. Once you flash a custom ROM, or even just install recovery, NEVER accept an OTA, it could potentially brick you phone (although most likely it will just fail)... Rooting along will not stop an OTA, but if you have modified any system file, it could potentially fail.