Tea with soy milk

Options
Heya folks! Just a quick question to all you guys who drink tea but use soy milk instead of regular milk - have any of you experienced an upset stomach after drinking it?

I used to use regular milk in my tea (+one sugar) but I'm slowly trying to include more vegan substitutes into my diet. I had my first cup of tea with soy milk last night and felt SO sick with tummy cramps all night. Same again tonight! I thought it might have been something I ate...but now I think it's the tea!

Anyone else experience this? :S