I had also started eating activa or danactive, it's the same thing, both supposed to help with constipation. It did sometimes help, but it did also make my belly swell. I know I'm lactose intolerent though; I decided to risk it because it wasn't much yogurt.
Anyway, I did see this medicine over the counter, at Wal-Mart of all places, that's supposed to be for IBS. It pretty much has the same things in it that activa yogurt has, except it's a pill and there's no lactose involved, just the live cultures. I haven't tried it yet, but I keep meaning to. (ha ha! I'm too busy even to worry about my IBS much!) It seems safe and worth it, though.
You can't believe all the hype on television. Activia is fine for people who don't have lactose intolerance, but a lot of people with IBS have gluten and lactose intolerances, too.
There are plenty of other ways to get fiber supplements if you find that Metamucil is too harsh for you, like it is for me. Psyllium fiber isn't for everyone. There are other types of fibers that don't have psyllium, which will often produce gas and irritates GERD for me and for other people, too. Benefiber is supposed to be good for some people. I've been using flaxseed meal for my fiber and it has proven to be a good source.
So, I would definitely stop the yogurt, because it seems to be causing you distress, rather than helping. It isn't for everyone. Too bad, because I like yogurt, too, but I'm one of those that would be affected the same way as you are.
When I went through an elimination diet, I was able to discover what a lot of my food sensitivities are. There are some big ones on the list that I was given that affect a lot of people with IBS and GERD. The two biggest ones are still gluten and lactose intolerances, which affect the IBS. Finding out what your food sensitivities are should help your IBS a lot.