Under armpit lump and chills what checkup should I do without making it obvious to my mom that I think I might have cancer. Do I have cancer? I'm 18

Less Likely. I think you should speak to your MOm right away and let her know what is happening to you. There are many other causes of a swollen lymph node in the arm pit (axilla) including and infection that needs treatment with an antibiotic. The less likely cause is a "cancer". Please see your doctor right away and also speak to your Mom.