Poor late game skill overall

I've come to this problem lately that even though I sometimes win the lane and I am for example 6/3/5 (adc main) when the late game starts:I just end up 6/11/10,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,mostly because of this:

1.I realise my farm is atrocious so I go to farm somewhere and suddenly someone/whole team comes and kills me 2.I just wandering to bot for example to push the lane just a bit and suddely BOOM :EVERYONE IS THERE OR THE ENEMY 3.I mind my own bussiness I go for red or blue let's say and oh what's that,you want that blue,enemy says.HUZZAH.....I am sliced in half. 4.I sometimes can't even step out of the base 'cause when I do i realise that enemy toplaner was willing to go AAAAAAAAAAAAL the way from top when i was pushing aaaand ......ye,obviously you can guess what happened

Please how to fix this,some helpful advice would be nice :) Thank you :)