iPhone 6+ Controls Itself..?

Hi! In December, I received and iPhone 6+ for Christmas. It was a really expensive gift, and it's frustrating that I'm already having a major problem with it. Everything that I try to do on my phone is interrupted! It operates on iOS 8.1.2, which I've never had a problem with until now. When I'm watching a movie that I buy, or watching Netflix/Youtube, the videos pause themselves. Not to load, they just stop. Sometimes, a different show or video comes on in it's place. The same thing happens when I'm listening to music in iTunes or Spotify. The songs pause, play, and skip on their own. And to make things worse, Siri activates itself constantly. I have no clue what caused it, it just started a few days ago and I haven't downloaded anything or messed with my settings. I've looked at all of the support forums of the people having a similar problem, and none of the things suggested have fixed it. (turning of shake to shuffle, turning off hey siri, and even turning off siri altogether) It would be really great if there was an inexpensive way to fix this, because like I said, it was a really expensive gift, and I've only had it for a little over 3 months. Thanks!🙂