Hello! I read carefully your query. If I were your treating doctor I would try to exclude the most common causes of these symptoms.In order to do that you need to do some studies. -Complete blood count to exclude anemia (low red blood cells and low hemoglobin) since you have a history of donating blood. -Blood sugar to exclude an hypoglicemia(low blood sugar) -Monitor your blood pressure to exclude a possible fluctuacion in blood pressure during the day. If these tests result normal I suggest to consult a physician foe further diagnosis and treatment. Meanwhile you should get some rest,eat healthy foods mostly green vegetables,drink plenty of fluids. Hope my answer has helped. Take care Dr.Rovena