IBS-D / Food allergy?

Hello everyone, I am new to these boards but I have been lurking for a bit! Last year around new years I got D for a few weeks and went to see a doctor. I was then referred to a GI specialist who did blood and stool tests and everything came back normal. I was about to have "invasive tests" however, towards the summer my symptoms just stopped. Since then I have had normal BMs everyday, once a day at the same time and it was a blessing. However.. Last Friday I got food poisoned and it was hell, I had D for about the following 2 days and intense nausea. This ended on Sunday, so I started having regular foods again along with well formed BMs with no D. However, last night I bought some soy milk from a convenient store and as soon as I drank it my throat started itching like no tomorrow and I stopped drinking it. Now I'm sitting on the toilet again, having D. I had a little bit of nausea this morning but a normal BM, however some of the stool was very soft. After that I started having the runs (sry to be graphic but it was watery with a cloudy liquid) Does this sound like post infectious IBS or was it because of the soy milk (note that I usually dont get an itchy throat, something might have been in this soy milk that got me!) Any ideas would be great, I have a lot of work due in the next few weeks and I need to be healthy!