Q: my phone keeps crashing on every app

the main problem with my iPhone 6 is that it keeps crashing on every app i try to open. It's only been happening the last week or so, i took it to an Apple store close to where i live and all they said is that 'have i tried restarting it by pressing the Home button and power button together?' i replied yes, about 48 times a day. The second thing they asked was 'have i backed it up recently?' i replied with i attempted to, but my iPhone rejected my laptop. The problem is not with my laptop, it is definitely with my phone because it has also forgotten my security details. This includes all of my Touch ID codes, my Apple ID, and has logged me out of every single app, examples consisting of Snapchat, Instagram, Spotify, etc. It's getting to the point where i am constantly frustrated as even when i open simple apps such as Mail, my phone crashes and does not open the app. It also crashes when i attempt to enter WiFi passwords, and also rejects each code when i know for definite that the codes are correct. Help before i throw it out of the window please! It is just over 1 year old, on contract with EE, and has never done anything like this before. Thank you.