Aperson, relaxation is helpful, but research is showing not as helpful as the gut directed Hypnotherapy or CBT, this was discussed breifly in the last chat with the experts.
Distraction can also be helpful, which is usally what is happening when your reading or playing a game ect.. Really relaxing and and getting to homeostasis (balance), there is much more to it all. Its good your doing it, but you might find better results, big results a lot of times, from different methods. One of the most misunderstood issues in IBS treatments and causes.
Try one thing at a time. The multivitamin, I would think has calcium in it. So try that first and see what happens. If something goes wrong one time, you have to try it again, just because there can be a lot of reasons, perhaps other then the one thing your trying at the time.