Inflamed axillary lymph node when laying down

For a few years I've noticed that at times an axillary lymph node on the right side of my chest just on the side of the pec muscle becomes inflamed, causes pain, and is numb to touch. Sometimes the pain is bearable, but recently it's been extremely uncomfortable. I started noticing that the pain generally exists only when I'm A) laying down on my backB) lying down with pressure on my abdomen/pelvis (i.e. laptop) or C) laying down flat on my back with my knees extended out so that the heels of my feet touch the base of my thighs/buttocks.

I thought at first that this could just be some bacteria infection or something, but now any and every time I am in one of the 3 positions mentioned above the pain and inflammation starts. The inflammation goes away after sitting up. Sometimes during the day when I'm just standing I'll notice that this right axillary lymph node reacts more sensitively to contact, but it's nothing compared to the pain in swelling when lying down.

My questions are: What could be a cause of this? How are the lying position and abdomen/pelvic pressure connected to the pain?

A brief medical history:
-Male, 19 years old
-Taking minocycline
-Scoliosis
-Testicular cancer: right testicle was removed and tests showed that no spreading occurred. Also, my CT scans of my chest never showed anything on the right side of my chest

Thank you!