I just can't work out whether I am being silly or whether I need to be worrying. 
 

I am 40 and am breastfeeding my toddler at the moment. I noticed a big, hard lump deep inside my breast about a month ago. I presumed it was a massive blocked duct but it's still there. It doesn't hurt and I feel it mainly when I lie on my back and push up under my breast. It's maybe 2-3cm and not round or anything. I can't feel anything similar in my other breast. 
 

is this just normal for breastfeeding or should I get it looked at? Has anyone had anything similar? It isn't a lump in the breast tissue if that makes sense, it sort of feels like it's inside. 
 

Thank you for any advice or reassurance x