I have read your question,
You may be suffering with Pre-Menstrual Syndrome (PMS) This occurs in about 90% of women and it is completely normal and there is nothing to worry about.
Normal fluctuations in hormone levels are responsible for some of the symptoms most commonly associated with the monthly cycle, such as bloating
, breast tenderness or headaches
node sensitivity does not occur , Without physical examination it is difficult to tell .
The discomfort in the right armpit may be due to breast Tenderness and nothing more.
I recommend you to take a lot of fluids and light diet upto 5 times a day and try to take it in less quantity , during your periods.
I would also suggest you to consult a gynecologist for further advice.
Wishing you a good health,