For me, it was the other way around. I've had IBS all my life. The GERD reared it ugly head 2 years ago. It's strange, but when the GERD was bad the IBS soon followed. When I was having a bout of IBS, the GERD would start. I think they are related and it's not surprising since our digestive organs all work together. I do know that my IBS started kicking up bad the longer I was PPIs.
The calcium carbonate helped my IBS A LOT. It got me to the point where I didn't have to be afraid to leave the house anymore. I also take a probiotic. I'm not sure if that is helping at all, but I was able to bounce back from an intestinal bug much quicker than before.