I have IBS as well(plus I had my gallbladder removed in March) For me, it has gotten worse, but I don't have constipation at all, just diarrhea. Luckily I'm a stay at home mom, so I'm always close to a bathroom. I try to avoid foods that I know will trigger it, if at all possible. If it gets too bad on a certain day, I will take medication for it. Otherwise, I just deal with it.
It actually may be why I've been fluctuating in my weight so far. I'm just about where I was pre-pregnancy. I will lose a couple pounds one week, and then gain it back over the next.
I had asked my OB about the diarrhea, as I worried about not absorbing enough nutrients, but he didn't seem too concerned. He said we will just keep an eye on my weight. If I start to lose and not gain at all, then we will do something about it.