Stomach Pain after eating yoghurt and fasting?

So ramadan has started and in the morning for suhoor I eat yoghurt with some oats and bran. But by around 11:30 am I start to get these really intense stomach pains and it feels like someone is stabbing my stomach. Its horrible and the pain is overwhelming. After I go to the bathroom (sorry for the details) I start to feel better but then I become really gy. Is this due to a reaction to the yoghurt? Could I be lactose intolerant? Or is it just because I am eating yoghurt on an empty stomach and its causing this? I always eat yoghurt, but since starting fasting I am getting pains from it. :(