2 billion live cultures isnt a lot, thats like whats in yogurt. I'd suggest at least 15-20 billion. The antibiotics probably destroyed the balance in your gut. It takes time for that to heal.
Does your tongue seem to have a whitish coat covering it? If so, this a yeast overgrowth. this could be the cause for all your issues.
While apple cider vinegar can help, you first off, need to get unpasteurized, raw acv. And you take it with a cup of warm water. If you try to take it straight its probably gna hurt.
Next, cut out sugar and starch. Eat lots of fruit, veggies, fish, and chicken. Fruits are good, but only specific ones (strawberry, blueberry, grapes, and banana).
I suggest you add a smoothie to your daily diet, along with the citrucel and probiotic. In said smoothie I'd use all organic products. spinach, kale, strawberries, blueberries, carrots, and a tablespoon of raw honey.
Hopefully this will help to start balancing out your gut flora and should get you back to regular bowel movements, which should reduce the gas. And since you are having gas issues, just do a google search on what foods to avoid. I know beans, broccoli, asparagus, and brussel sprouts are on the list.