So glad you have some answers and a game plan! I have a friend who had a similar problem and was on a few different medications, the two you mention sound familiar, and she now has 20 month old twins. All the best to you!!
Just a warning about prednisone (in case you have not taken it before) - it makes you massively hungry! I always gain a bunch of weight not it, not so bad when you are pregnant but something to watch out for.