Lump on breast

I have had a lump on my right breast (closer to my armpit than my nipple) for a few months. It is very painful to the touch and pretty large. I've been to many doctors and have had ultrasounds. I've been cleared for everything. They say that I have dense breast and that I should switch bras to prevent irritation. I honestly don't believe that is the problem. I have been wearing soft sports bras for months and it is still painful. Anyone else experience this?