mobile

Hello guys, i'm having a problem ;f

I was on cm12 nightly when i decided to reboot my device after few days of running, strange thing happend and i ended up in bootloop.
I've downloaded 4.4.2/4.4.4/5.0.1 stock images and tried to flash it guided by the instructions in this thread, however i still get a bootloop, even after clean installation, even after wiping cache and doing a factory reset.. I've managed to boot up my device twice since yesterday, after getting stock image to work i pushed cm12 and gapps on my phone and flashed them.
At the first try, i got bootloop again, so i decided to go through the whole process again, many attempts later i've managed to boot up my device again, and again i decided to flash cm12 and gapps, this time my device booted up properly so i wanted to gain root access, in order to do so I flashed UPDATE-SuperSU.zip file and as a result end up in bootloop again.. I have no idea wtf is wrong with my nexus. I am still trying to flash factory image, and i always end up with bootloop.. I'm out of ideas here, HALP! ;(
@update:
I have uninstalled all drivers, and mount my device to another usb port, then with NRT i installed google's drivers, by using nrt i have flashed 5.0.1 factory image, rebooted into recovery and wiped/factory reset, after that i rebooted my device and still no luck - hanging on floating dots for 15 minutes..
Before all of this I tried formatting my cache to FAT and to sdf4 and it didn't help, I literally tried every single instruction i could've found ;/
What's wired is that when i encountered bootloop yesterday and wiped/factory reset i booted fine, after restart it went into bootloop again, so i thought i would wipe/factory reset again i'll be good to go, but.. it didn't help this time oO

things i've already performed:
1. fastboot oem lock/unlock
2. wipe data/cache/factory reset
3. flash factory images of 4.4.2/4.4.4/5.0.2 through NRT/manually
4. converting partition to fat and next to sdf4
5. reinstalling drivers
6. i even tried switching motherboard from my old n4 and i still stuck at bootloop *LOL!?*
7. after 6 i thought it may be related to usb port so i switched usb port from my old n4 and it did help but.. until next reboot ;/

from time to time, after flashing it boots up just to make my hopes and then it gets the bootloop after restart ;/

Thx in advance for your help..
p.s. sorry for the new thread but in "how to flash factory image" noone responded