My skin was HORRIBLE when preg with my son.
I'm sorry to say that nothing helped. It was hormonal, and the only thing that fixed it was not being pregnant anymore.
My best success was to do a night hot compress on the most broken out areas. It at least draws everything towards the surface of the skin, so anything you do use topically will have a better chance to work.
For the record, I used BP and Sal Acid throughout 2 pregnancies with no issues. They're both safe.
Mario Badescu makes a product called Buffering Lotion (containing Sulfur) which did wonders for the cystic acne that I had.
www.mariobadescu.com
It worked when nothing else did.