If bread bothers you but pasta or cake don't, then you may have a yeast intolerance/sensitivity...
I have antibodies to yeast (both brewer's yeast and baker's yeast), and I notice that I don't feel well in my stomach when I eat yeast-containing bakery goods.
Comments on the testing for food allergies:
Skin test result accuracy depends on the concentration and age of the test serums used. The test serums are not standardized, so you may react at one doctor's office, but not at a different doctor's office if they each use different test serum concentrations. Also, the proteins in the test serums can break down over time, rendering them unable to elicit an allergic response even in individuals with known severe allergies to what's being tested. If a person has anergy, then they won't react on a skin test...anergy is caused by an imbalanced immune system (commonly seen in those with certain autoimmune disorders). This is why they have to put the histamine and saline controls on you when they do the skin test...if no reaction is seen to the histamine (i.e., anergy), then they know the test isn't going to be valid. Also, if a person is taking antihistamines, then this test will likely not be accurate. Blood allergy tests and the other tests mentioned below are not vulnerable to the effects of antihistamines.
Blood tests (RAST, CAP-RAST) can miss allergies for the same reason as skin tests can. And also they can miss allergies because the tests are designed to detect one configuration of protein for a given food but there may be many different configurations (i.e., different protein configurations of the allergenic proteins in the food) or possible proteins.
My allergist explained it like this...say a wheat protein looks like your hand. The RAST or CAP-RAST blood test may be able to detect an antibody that sticks to the thumb, but not to any of the fingers on the wheat protein. So if a person's wheat antibodies aren't "thumb-shaped" then their wheat allergy test won't detect their allergy to wheat, even though an oral challenge proves the allergy.
There are other tests less well-accepted:
Blood ELISA IgG/IgA/IgM allergy tests (not sure if these are FDA-approved yet or not, but there has been a lot more research on this type of testing recently, especially in the setting of Irritable Bowel Syndrome). These test for delayed hypersensitivity to foods. I've had such tests done twice (IgG testing is most common, but the others are available from certain labs) and got slightly different results both times. They tell me these tests aren't accurate if the person isn't eating the food tested regularly, but I have antibodies showing up on these tests for foods that I haven't eaten in years (example = oats...I get very nauseated from oats, and haven't eaten oats in over 5 years, but I test positive on the IgG & IgM for oats). Unfortunately, the labs doing these tests often don't test foods that are not eaten commonly...such as arrowroot, millet, etc., so if you already eat a non-traditional diet, the test may not be as useful.
ALCAT tests (I don't think these are FDA-approved for allergy testing). Another blood test that can detect supposedly any kind of antibody to foods. I have not had this testing done, so I don't know much about it.
Electro-Dermal Screening. Not FDA-approved for allergy testing, but this testing method can reveal intolerances, hypersensitivities, & allergies. The premise of the test is that acupuncture meridians will show energy flow changes when the person is in contact with the foods that cause their body to experience problems. I personally think this method is more subjective than blood testing for allergies, but also it is not limited by the available test foods - you can be tested for any food you can hold in your hand.
A variant of EDS is applied Kinesiology testing (muscle-testing) - also not FDA-approved for allergy testing. It is used in conjunction with NAET by some practioners. The premise is the same as for EDS, except instead of a machine measuring energy flow on a specific acupuncture point, the practitioner pushes on the patient's arm while the patient tries to resist and this is done while the patient is holding the test food in their other hand. The theory is that the muscles used to resist the pushing on the arm will go weak in the presence of foods that are not "healthy" or "beneficial" for the patient. I think this method is more subjective than the EDS method of testing, but it does not require special equipment to perform, and thus can be used in a grocery store when one is looking for something new to try.
Another variant is dowsing - also not FDA-approved for allergy testing. The person holds the test food in their left hand, and the practitioner touches the person's right side (shoulder or hand, usually) and swings a pendulum to "dows" for whether the food is compatible or good for the person or not. Some think this is a little too out there for them, but one of the advantages to this method is, if you have a good dowser, it can be very accurate. Also, if the dowser has a "witness" (film photograph, writing sample, piece of hair, etc.) of the person, they do not have to actually be present for testing to occur...so it can be done remotely.
Stool testing (EnteroLab.com - I have no financial connection with this company) - a new form of allergy testing is looking in the stool for antibodies to certain foods. This type of testing is very new, and not much is known about the limitations of this type of testing. I got my Gluten-Sensitivity diagnosis from this method, and they also were able to test for egg, yeast & dairy sensitivities.
I've experienced all of the above except ALCAT, and the testing that I find most accurate is dowsing and EDS. Both methods have told me that there are only a few foods in existance that don't bother my body in some way or another.