Before all of this happened, I rooted the phone with IORoot, tried to flash CWM (I think successfully), but was not able to install CyanogenMod, so I flashed an earlier build of the stock OS (D20010o), rooted it again (I'm not sure that I had to--I think it stated that my phone was already rooted), tried to flash CWM again (unsuccessfully this time), and I gave up. Then this problem occurred.
Every time I try to power on the phone, the LG logo flashes, and the screen stays on, but it's black. If I try to do a factory reset via the hardware buttons, I am able to see that screen, but as soon as I follow the instructions of pressing the power button twice, it says that it's initializing the reset, but then the phone's screen goes black again--not sure if the screen is on or off, though. The LED light is also not on during any of this.
I'm unsure what to do. I've had the phone for about 6 months, but I had not owned an Android before that--iPhone user for 3 years. I obviously did not do enough research or ask enough questions, but I would like my phone to be in a usable state. I would greatly appreciate any help that anyone can give me!