You can use Benzoyl Peroxide and Salicylic Acid during your pregnancy.
That said, your acne is probably due to hormones, and very likely nothing you do will improve it. I had TERRIBLE cystic acne with my first pregnancy. (never had a skin problem before it) I tried every product, every combination on the market that I could get away with. Nothing made a dent. Not even a little. It didn't improve until I went back on the pill 8 weeks after birth.
It's incredibly frustrating and you feel so unattractive. I know. You can drive yourself crazy with trying things, but unfortunately, nothing will really work. It's hormonal, not bacterial.
I used (and still do) the acne products from Mario Badescu. I found those, of all of them, to heal big breakouts the most quickly. They never kept the away, but they got rid of them faster than other approaches.
Sorry to bear the bad news. :(