Oh my, you were getting headaches within 30 minutes of taking just one tsp?
Can I ask what exactly the label says? I am concerned about the quality of this DE. You want the kind that says "Fossil Shell Flour, Perma-Guard, Food Grade." If that's definitely what you have, then perhaps we need to look at time of day, whether you're taking it with food or on an empty stomach, etc.
Or another option would be to wait on taking DE until you're further along in your cleansing process. Might want to start with taking a small amount of therapeutic clay daily for a few months first. If so, get the Earth's Living Clay brand calcium bentonite. It is more effective by far than conventional brands available at health food stores. That's the kind I use, because if I'm going to eat dirt, then I need to know for sure that it's doing something good for me
http://earthslivingclay.com/TLC_PRODUCTS.HTM