Instant pain following ingestion.?

I woke up this morning feeling fine. I was feeling thirsty, so I grabbed a gl of soy milk for myself. (I'm not lactose intolerant, I just like the taste of soy milk) However, the very instant I drank it, I felt crippling pain. I actually doubled over. The pain came far too quickly to have been caused by 'bad milk'. It wasn't 'what' I was ingesting, but the fact that I 'am' ingesting. Every time I drank more, I would feel the same pain. However, once the pain was gone, it stayed gone... unless I drank more.