If anyone has any thoughts on this, I'd appreciate your input:

A mother is nursing a toddler, usually only at night time.  She nursed her
first child to age three with no problems and has had no problems with this
one.  About a week before her period is due her breasts start getting very
tender. The nipples are very sensitive and painful when the toddler nurses.
 Breasts are also sore elsewhere and she thinks they look a little larger.
 They are sore enough that she can't sleep on her stomach comfortably.  There
has been no change in the toddler's nursing pattern.  The mother thinks she
must be pregnant because her breasts have never gotten this sore except when
she's pregnant.  But right on time her period starts.  It is now day three of
her period, which seems to be a normal one.  Her breasts are less sore, but
still tender.

The mother has no fever, no red streaking, no unusual lumps (she has
fibrocystic condition so they're always somewhat lumpy).  No signs of yeast
infection that I can tell.  The toddler has no thrush in his mouth, although
he did complain of a sore bottom, but the mother says it was just a little
red around the anus for a few days.  She just put some diaper type medicine
on it and it's better.

Any ideas?  TIA

-Lucy