expressing milk & engorgement

Due to me skipping a 12 hr expressing, I have some engorgement up till my armpits. So I have been trying to express out every 3-4 hour for 3 times now, and still continue to do so. I massage at least 10 mins up till my armpit area before pumping at least 30min (sometimes even up till 45min). I do feel that my milk is reducing but the lump near armpit still exist. Am I doing anything wrong? How should I reduce the lump near armpit??