What Causes Stomach Pain After Having Rice?

Recently I have started getting diarrhoea, I believe I have narrowed it down to when I have a chinese takeaway. I had a chinese takeaway last week and about 2-3 hours later, I started getting pains in my stomach/bowels and required the assistance of a toilet so I could relieve myself. I spent a good hour on the toilet before I feel better but I will be fine the next day. I had chinese again today and the same thing happened. I have noticed that the sweet and sour chicken balls seem to have had a different taste recently. I have used them in the past for a year or so now and haven t had any problems until now. In the past when I was younger I found that eating rice caused me to have a tummy ache and needed to relieve myself. I was wondering could I being having an allergic reaction to the rice or could it be some kind of food poisoning? My family has chinese takeaway at the same time and they are unaffected.