What could a swollen lymph node in my right armpit that I've had for over 6 months mean if I also lost 10 pounds in same time unintentionally and don't sleep normally due to studying habits?

There are quite a few things it could be. Usually swollen lymph nodes are a sign that your body is fighting an infection, and from the sounds of it you are stressed out which lowers your immune system. However, if it has been going on for 6 months then it could be a cyst (most are benign). I would go to the doctor and have it checked out to be sure though.