For some people, there is a period of time when you begin a probiotic that you experience extra gas. Bacteria do create gas, so it may take time to adjust–especially in a system such as yours where there's already an issue. Since you seemed to have an easier time with low-potency probiotics, you may want to try one of our lower-potency formulas and then gradually work your way up to one with a higher potency.  FloraSMART, for example, comes in a 6 Billion formula so that may be best, then you can work your way up to the 12 Billion formula. 

Keep in mind that an average adult will have tens of trillions of bacteria in the gut at any given time, so a few billion more every day is just a drop in the bucket. Yes you can take too many, but when that happens the result is typically diarrhea, which occurs to simply flush out the excess. It may be appropriate also to see a naturopathic doctor and work with your diet in addition to adding supplements. The types of food you eat often play a significant role in the development of symptoms such as excess gas and bloating. Good luck!