Constipation

Rosie • Can't wait to be married to my King 💍👰🏼 December baby on board 💗💙☺️
Hi girls hope you're all well
. Just a quick one, 
I've been taking Ondanstron for hyperemisis for a while now it is a miracle drug however nasty side effect! Consitpation!!!! 
A few weeks back I was literally in agony and hadn't been for 2 weeks. I haven't been properly for about a week now. 
I've tried everything from diet, exercise Lactoluse everything I've tried. 
But I've just read online about Movicol (UK) or Miralax (US) and wondering has anybody had this and it's worked and if so was its safe. I was told in the hospital not to take unless emergency but my own doctor said it was fine as it's not absorbed into the blood stream. 
Quite a few online forums also says it's safe so should I try it or? 
I really need a solution that will work because the feeling is dreadful. 
Thanks in advance! X