I get pain in my underarm/ upper breast area. any idea of whether it could be breast tumor?

Probably not: Pain under your arm and in your upper breast is probably not a breast cancer. Pain in the breast is very common. If it comes and goes with your periods, i'm reassured. If it is constant or worsening, you should see a doctor. There is a rare type of breast cancer called inflammatory breast cancer that causes severe pain, redness, swelling, and skin dimpling, but your symptoms sound more mild.

Need examination: You should see your md for further evaluation. It is not easy to say something more accurate without examination. Pain in underarm/upper breast area- could be caused by painful enlargement of lymph gland on the armpit for instance- perhaps related to shaving etc. Or could be infection/boil etc. Pain as first presentation of beast ca -eventhough happens- not too common. See your md for evaluation.

Need to see a Dr: This is a hard question to answer without being evaluated in person. You need a complete clinical breast exam. It is possible that you need a mammogram and ultrasound. Contact you pcp and ask to be referred to a breast surgeon or a breast center for complete evaluation.