Headphones get unplugged

Hello, I have Two Audio Type Problems With my Computer! And if you can Help, be more than happy to reply!

Soo! First! When I plug In my head phones it Says "You Just Plugged a Device into the audio jack" Then BOOM a Second later it says It has been Unplugged, wich it HASNT! And When I put my headphones in a certant angle it Works! But I tried Multiple Sets of Headphones And its the same! Please Help me!
NEXT! When I turn on my computer, My sound Works FINE! Then BOOM a few mins later, my Sound Doesn't Work! I adjust my sound over and over But it Just DOESNT Work! Please Help Me! I really need Help!
BTW- I use a Dell Windows 8.1 64bit