Hi, I Am A 18 Year Old Girl, And Overweight.

Hi, i am a 18 year old girl, and overweight. I have been having this severe pain in my left armpit and left breast for a couple of days now, and also my arm feels abit numb. Also my armpit feels really swollen and hurts to touch. Im really scared its cancer i have checked for lumps but its hard to tell as they are quite lumpy/fatty anyway. Please help