I don't eat wheat at all, as it is high in carbs. My diet mainly consists of atkins products, meats, cheeses and vegetables. Thyroid would explain the constant feeling of being cold, however it wouldn't explain the difficulty in breathing. With pre-diabetes, it would make sense if I was overweight or if I ate mostly sugars, however in the low carb diet, the only sugars I intake are alcohol sugars such as aspertame(low amounts) or maltitol.
The year before I started having these problems, I was at an arts middle school for vocal, and I still do the occasional singing in the shower and when I'm alone.
When I feel the shortness of breath, I don't notice it until I try to take a deep breath, and it's almost as if my lungs don't expand enough, and then I'm forced to exhale. That is followed by dizzyness, and then rapid heart rate, then afterwards its followed by the feeling of tightness in my throat-what I'm assuming is due to the anxiety that the inability to breathe brings.
If you haven't had your thyroid tested, you should have your thyroid tested. Another good one to check would be the A1C to make sure you aren't dealing with diabetes or pre-diabetes. The thyroid would be my biggest concern, because that may be why you can't lose weight. Also consider going gluten free: http://www.rodale.com/wheat-free-diet-0?page=0,0&cm_mmc=Twitter-_-Rodale-_-Content-RecentNews-_-modernwheatfarcry
I'm only guessing but hopefully offering some sort of information on where you can look. By the way, my mother said the same thing about me. It turned out she was wrong, too.
Consider looking into Vocal Cord Dysfunction. I haven't heard of it causing anyone to pass out, but I was diagnosed with this and sometimes feel like I can't really get my breath. It literally has to do with the vocal chords doing the exact opposite of what they're supposed to do. They're supposed to open up when you take a breath in. I saw it on the camera for myself. Mine will do the exact opposite. There is controversy about how common it is, but it is more common than what many people think it is. If you at least knew what was happening to you, it could help calm you down even when you're having symptoms. Vocal Cord Dysfunction is uncomfortable but it won't kill you. I'm to go for speech therapy, but I'm waiting to hear back from the place for the sliding fee schedule. They teach interesting and different breathing techniques that are supposed to help make the vocal cords do what they're supposed to do.
I only take one 200 mg of vitamin B12 a day, along with 400 mg of folic acid, and one tablet of vitamin C...I can't currently remember the amount that one is in. I am not taking a multivitamin.
I would go to the doctor, but, like I said, my mother refuses and insists I'm a hypochondriac. Since she currently still pays my insurance... I'm kind of out of luck for now and I guess I will have to wait..
OOps, too soon,
Remember, while there is a lot of information on the web, it's important not to diagnose yourself. Because while yes, you do know your body and you know when something is wrong, a doctor uses clinical test to help rule out a lot of different things and diagnose you. It's also very easy to mistake one kind of diagnose for another -aka headaches, nausea, and cramps could be the sign of a period or a pregnancy.
How much vitamins are you taking? And are you also taking a multivitamin. It is possible to too much vitamins.
Honestly it sounds like you really should see a doctor. I'm not sure what's going on but serious problems do need to be ruled out.