Um, at the risk of being too personal ... are you constipated? Seriously, a bowel distended by a ball of hard, dry stool can and will cause painful spasms in its effort to expel the mass. At best, it's uncomfortable until the mass is finally eliminated, but if it continues, the condition can progress to a situation known as
impaction which is serious, and requires urgent medical attention. Yes, constipation is associated with stomach upset, nausea and headaches. And just generally feeling awful
Have a read through the article
Low Carbing and Intestinal Health, which you can find by clicking on Low Carb Tips from the orange menu bar near the top of the page. There are some suggestions that may be helpful, if you think The Big C might be a problem for you.
For some people, the change to LC eating from previous ..... especially if previous was a lot of refined "white" foods like bread, bagels, rice krispies, special K and pastas ..... can precipitate a few weeks of intestinal "rebellion".
If the pain persists, and you continue to feel unwell overall, a trip to the dr. is definitely in order. If you have a fever, or if you're vomiting, don't wait, get to the dr. ASAP.
Hope you're feeling better soon
Doreen