Hi - I'm currently researching Celiac's Disease as I believe I might have developed a Gluten intolerence over the past year (possibly longer). What I'm learning is that CD can produce a wide variety of symptoms (including some that you mention) or none at all for some people. There are several types of tests but some can produce false negatives and I read that 97% of sufferers are undiagnosed/misdiagnosed with it taking on average 4 years for some people to be correctly diagnosed.
Having said that, I've read that many people diagnosed with IBS actually have CD. CD can cause diarrhea or constipation......among all sorts of other things...gas, bloating, joint pain...
Like you, I've been trying to research and confirm some of my symptoms which also include insomnia and light sensitivity. I haven't been able to find much concrete evidence on these two but a lot of CD people are asking questions about them. I haven't been diagnosed with CD yet but have been cutting back on gluten to seek relief and it seems to be working. (good advice above about elimination diet, and soy can be a problem for gluten intolerance also.)
I'm almost certain that the intense insomnia and light sensitivity that I've had over the last year are related to gluten. I would suggest that you look at Celiac's disease. I hope this helps you!
http://www.celiacdisease.net/
The other issue to consider is that you have undiagnosed migraine issues on top of IBS issues. You can have both. I do. GI symptoms are associated with migraine disorder, too. I believe you should ask for a referral to both a neurologist and a GI doctor.
Definitely the elimination diet that Matthew suggested. That is a very important thing for IBS sufferers to do. And, food sensitivities will affect migraine disorders, too. In fact, it isn't surprising that most of the same things affect both conditions.
Very often SSRI's are prescribed for both of these conditions as well, but I believe you may be describing migraines as well as IBS.
I would start a elimination diet..worth a shot...
I had the WORST nausea, anxiety..upset stomach, IBS issues and I went 2 weeks on eating pears/turkey/meats without flavoring/white rice..and my nausea and severe anxiety went 90%. Turned out it was soy that was getting me. A common symptom of food intolerance's is anxiety..sometimes insomnia because of lack of vitamins due to malabsorbtion (basically you're not absorbing nutrients because of a food allergy or intolerance)
So I'd give that a shot, now i'm just dealing with bad IBS :(...good luck!
When they did the blood tests, did they test for autoimmune diseases, such as Lupus? Have you been tested for MS?
If it is an anxiety disorder, getting the right anti anxiety and/or antidepressant will make a huge difference with your IBS, too.