I'm honestly nervous

two weeks ago the right side of my neck started swelling and went down to the collar bone, I also feel a swollen...flat lump under my collar bone. trip to the er we go and they found enlarged lymthnobes deep in my neck via ct scan and a medium sized black mass in my lung via xray. I've been extremely tired, sometimes arm pain and have trouble breathing (everything gets worse at night). The er doctor seemed really concerned and put me on a week of antibiotics and told me to contact my GP asap.

I'm extremely worried it could be cancer, my blood count was normal so it's not any white blood cells fighting a infection and the swelling doesn't hurt. It just feels like a pinched nerve. Every day it gets worse and I'm afraid. I'm calling my GP tomorrow asap and I'm worried sick. Could it be Lythoma???