keyboard and trackpad stop working after login

Macbook air mid 2013 1.3GHz i5 8GB 1600mHz

OS X Yosemite

a couple of days ago my macbook crashed. i tried to turn it back on but it was being very temperamental so, as it was late at night, i left it to recharge and have a little rest...

the next day i turned it on with no issues, got to the login page and hapilly used the trackpad to navigate to my admin profile then typed my password.

when it logged in, my curser jumped to the top left of the screen and the trackpad and keyboard became unresponsive.

the computer suddenly started looking for a bluetooth keyboard but i have never had one or connected one so not sure why it did this.

i have tried the SMC & PRAM resets as well as updating OS and also reinstalling Yosemite and nothing.

the only other thing I've noticed is that, when using the keyboard viewer to type, I'm unable to put on capslock. it is not grayed out like other keys are when pressed but it just won't work.

to me as a non-programming savvy guy, this looks like a software or programming issue but i can't find any answers online beyond what I've tried already.

Any help would be amazing