Macbook Pro screen glitches, 3 beeps, NOT THE RAM

My Macbook pro has been having screen glitches randomly with lines appearing on the screen and then it suddenly shuts down. Sometimes It beeps 3 times (what everyone claims is a ram issue) and sometimes it does not beep and will just start right back up again. I'm currently using it right now and it seems to be okay but this is always the case. It works fine and then all the sudden it glitches and shuts down. I

I have had the Ram replaced TWICE and have had the ram readjusted in case it has fallen out of place. my computer has passed every hardware test imaginable. Sometimes when I scroll on safari, chrome or anywhere (when its working) the screen glitches and lags really bad. MY computer is literally unusable. I am in nursing school and my computer is vital PLEASE someone help me!!!!

Here is just some details and extra info about what I've tried and researched:

I am currently using it in "safe boot" mode and I turned the SMS (sudden motion sensor) off.

I have done so much research on this issue here is what I have found thus far, obviously the ram issue, A GPU issue, A logic board issue (lets pray its not), a battery issue or a issue with Mavericks. Could it be something I downloaded?

Mac details:

13 Inch MacBook Pro Mid 2012

Processor: 2.5 GHz Intel Core i5

Memory: 4GB 1600 MHz DDR3

Version: 10.9.1

Graphics Intel HD Graphics 4000 1024 MB

This is what it says under SYSTEM INFORMATION Hardware>Memory.Memory Slots:

ECC: Disabled

BANK 0 / DIMM0

Size:2GB

Type:DDR3

Speed:1600MHz

Status:OK

Manufacturer: 0X02FE

Part Number:0x45424A3230554638424455302D474E2D4620

then it has BANK 1/DIMM0 and basically says the same thing