Hello! Dizziness, fatigue and nausea can be symptoms of pregnancy. Early stage of pregnancy may have other symptoms like vaginal discharge, tenderness of breast. So if you have these symptoms too it s more likely you re pregnant. Anyway, since you re trying to get pregnant i would suggest a to take pregnancy test. Dizziness and nause are common signs of different conditions from ordinary flu to brain tumors, so it s difficult to give you a more detailed answer based only on such little information. If the symptoms persist or get worse you should consult your doctor. Regarding allergies, nausea is not a common sign of these conditions. Food intolerance causes also problems in the intestinal transit. I hope i have been of help