That was my first thought too, have you changed to a new bra? I always found I would get horrendous blocked ducts when changing to underwire or a tighter bra.

Have to agree, if its a possiility to then I'd be expressing an extra time at work too, perhaps the expressing isnt clearing as much out as your bub would?

Just yesterday, I was thinking about this and why it happens after such long periods between or after what seems like nothing has changed. Hang in there, you are doing a wonderful job, it cant be easy.