Not sure how much help this will be, but I used to have asthma (I grew out of it!!!) and found that the asthma preventer inhaler (of which I had a few lying around for yeaaaaaaaaars but then I ran out well after my prescription expired) was THE best thing in the entire universe for getting rid of a persistant cough that refuses to go away. Only needed a few days of taking it, too. I've got a cough like that now and am out of those inhalers so on Monday I'm going to attempt to get a prescription for one. The other half is about ready to strangle me, I've been coughing for over 2 weeks. It wakes the baby up too

Short term, anything with codeine in it will stop a cough dead but I'm not sure if that is safe when you're pregnant. Doesn't say it is an issue for pregnant/breastfeeding on the box though, but it is addictive so you can't take it too long.