What Causes Pain In Chest While Breathing?

I have pain when breathing in and also with movement in my chest, behind or in my breast. I can t tell if its inside my breast or behind it? When I do a breast exam there seems to be a large area that could be considered a lump but its squishy and fibrous, not hard. Not sure if the pain is coming from the breast or behind the breast in the chest wall. No other symptoms but the pain is most intense when breathing and when sleeping and trying to find a position where it doesn t hurt.