Rice milk - An experiment

Yesterday I did an experiment with eating rice milk. In the recent past I have been having rice milk warm with either cornflakes and as porridge, and both times I got stomach upset afterwards. My mum suggested that maybe it is the heating of the milk was the problem and not the cereals, so try it cold. So, yesterday I had cornflakes with cold rice milk. The result - no problems. There was a few seconds whilst making my bed that I thought I felt a slight stomach quibble but it settled. I was fine for the rest of the day. No pains, no anything. So, maybe my mum is right in saying that heating up the rice milk does something to it that disagrees with me and my v sensitive stomach. If that is the case, then I won't be able to eat porridge with rice milk again or I shall have to find another milk to try. I have tried most other milks so far. I shall try it again on Tuesday when I'm not going out to see what happens then.