I have the same problem ( for over 11 days )
My doctor gave me some drug ( safe to pregrant women ) , you can buy from 藥房 ($50 a box ?? --for 50 packs ?? --- i don't remember the price and how many pack in one box )
Forlax Macrogol 4000 10 g
i take 2 packs per day now ( I'm 38 wk )
i hope it can help you .