Lumpy breast during periods. Tis mt!

I have noticed a portion of my left breast is little lumpy at the inner edge and below the nipple, it is soft and lumpy in 2 3 places soft to touch looks like a connected tissue sort of or maybe it's the outer breast bone but it's bumpy tissue like. I cannot see it from outside. I am in my 1st day of periods.I have never noticed this before. Not sure how long it's there. I can only feel it whn i lie down , whn i press the breast while sitting i cant feel anything inside and both breast feels similar. I have a slight heavier right breast and i can only feel this bumps if i dig really deep but not so easily like that of the left.but i have noticed similar structures on both whn i lie down slightly more prominent in the left since i have smaller breast. I noticed this yesterday. Today i felt the breast more tender and soft overall including the lump but i can feel the lumpy tissue at the edge and below the breast.The breasts are extremely tender in other parts.my periods is delayed tis mt