Backup password seems to have been changed

I'm really irritated with Apple and iTunes right now. I'm not sure what happened, or what it's related to, but my iTunes encrypted backup password somehow changed. I'm the only one that uses this computer, in fact I'm the only one is the house. When I first was asked to set a password for encryption, I set it and put it into my password program for keeping. I'm been using the same one since and I don't recall iTunes making me change it for some for some type of character/symbol/numeric/upper case requirement. I wouldn't have changed it for no reason. I actually had used that password to use one of the software products out there to check and make sure my backup had what I wanted and also to save my voicemails before I went to the iPhone 6. Has anyone ever had problems with iTunes saying your backup password is wrong when it's likely not? What, if any, are the password requirements? If it didn't ask me to change it for some reason, I NEVER would have changed it and not updated it somewhere. Also, I've tried all the likely combos that I would have used with some of the usual requirements for other sites, etc. I'm really angry because I wanted to backup my phone and reset it because the phone has been AWFUL. It's slow, it doesn't take my touch for clicking on things half the time. I'm really about to throw the phone, iTunes, and Apple technology in general out the window. This stuff needs to at least work somewhat as advertised. This is the 5th iPhone I've had, and BY FAR the worst.