don't panic!
it sounds like your graphics driver got borked after the last update. happens.
you rcomputer is healthy, it just can't boot to a graphical desktop atm.
next time you boot, instead of logging in, try pressing Ctrl+Alt+F2 - does that bring you to a text console where you can log in with your normal credentials (this is largely the same as booting to recovery mode)?
if so, please post the output of
Code:
lspci -k | grep -EA5 'vga|3d'
sudo cat /var/log/Xorg.0.log.old | grep -C5 EE