This sounds alot like me, I haven't had the weight loss really, but my doctor also suspects inflammatory bowel disease with me. As for the light-headness, I would ask your doctor about your blood pressure. I myself have been told recently that I have naturally low blood pressure, which is good, but because I have some other things going on, or just standing or sitting for long periods of time causes my blood pressure to drop..for most people this isn't a problem. Although for me I experience symptoms of the blood pressure dropping which is light-headness, dizzyness, headache, and feeling faint. Some people just experience symptoms of it. With me its also more often related to my stomach problems. So I would ask about that.
If not that maybe malnutrition is your problem, if your losing all this weight it could be because your body isn't getting the nutrients it needs from the foods your eating which could cause the body to shut down and feel tired and light-headed.
dehydration could be another cause of feeling light-headed and faint, so make sure your drinking water throughout the day.
I'm no expert but I hope this helps. Just what I know from personal experience.
I have chrons but not the feeling in my head. There is a blood test that can show if you have the chrons gene. This should tell you if you have chrons. You can also have both.
Good luck
Jayne