This happened to me, first with Liam and now (since 5 or 6 days ago) with Skaja. Liam was always a fussy, fretful feeder so my supplies were quite low anyway, but I did get a build up and found that a cup of sage tea a day for about a week helped. Also, I would only hand express (I found in the warm shower was easier), just to a level where I felt more comfortable (read - could bear to put a bra on). Skaja was a little different - she was feeding between 2 and 3 times a day and suddenly just stopped. Again, I am reduced to had expressing and sage tea!!! On the up side, I really fill out a bra now!