I usually have one of those large Activa or whatever yoghurts and don't have any of the symptoms you describe...
Are you eating lots of fibre & veg? That can cause flatulence, especially when combined with lots of real ale...
Picture the scene: An early autumn morning, in a field packed with tents where people sleep after a beer festival. The peace is shattered by a dawn chorus of trumps and creaks, somewhat reminiscent of the sounds of courting frogs in spring.