Password keeps getting changed

So my password keeps getting changed out of nowhere. I keep changing it to another password, but then a couple of days or weeks later it gets changed again (I Get notified by mail) and I have to use my password for example to download new apps on my iPhone (instead of Touch ID) or connect to iTunes on my MacBook. It is really annoying and it's definitely not someone who knows my password, because I keep changing in to another one. I was wondering if anyone else has this problem and if Apple could do something about it.