What Causes A Swollen Lymph Node Behind The Ear?

I have had a swollen, firm, non-painful lymph node behind my ear for at least 6 months. Had CT scan done on neck by ENT and he said there is a 6mm cyst in lymph node area. I have had night sweats nightly for almost 3 months. Have tried changing temp of bedroom and have even moved in past 3 weeks to a new house. Blood work is fine. ENT just wants to watch node. I am thinking that with the night sweats and fatigue, it should be biopsied and not watched. I have Crohn s disease, but have never been on Remicaid or any of the other cancer causing drugs that I know of. I have also started experiencing constipation, which having crohn s, has never happened for me. Also have tiny red dots that are multiplying each week. They are under the skin, although some are becoming raised. I have had tons of tests, but no biopsies. I am 29 years old and 98 lbs. I have not lost any weight. In fact, I have gained about 5 lbs since this began.