Q: iCloud Locked / Can't turn off / incorrect password

I have an iPhone 5C, it is currently running IOS 9.3.1. I have been having a fair few issues with the phone over the past 12 months and have finally had enough. I have reset my password that many times, I have now run out of Password ideas. My phone constantly pops up with Apple ID Verification and everytime I enter my iTunes / iCloud ID and Password, it says the password is incorrect. So I go through the security questions and change my password and it does it again and i've been dealing with this over and over and over for way to long. I'm ready to destroy my phone. PLEASE HELP ME!!! I can't even turn find my iphone off, however my device doesn't even show up in iCloud when I log into on my computer and hit Find My iPhone.