Underarm lump becomes more tender around menstruation

I am a 17 year old female. Some years back I noticed a small bump under the skin in my armpit. It's not noticeable when you look at it, but it is a little tender when I touch it. However, it's only when I touch it. It becomes more tender around the time of menstruating but other than that I don't feel any pain. it has maybe gotten slightly bigger since I noticed it, but it's no bigger than a pea. I had an exam last year, and the doctor felt around that area but didn't feel it because she was only tapping lightly. I forgot to make sure she really checked that area unfortunately because I am terrified of doctors. I'm supposed to go to the doctor in May for my check up. Should I go to the doctor sooner than this or is it fine if I wait another month?