exhuastion and dizziness is because of anemia due lack of ability of blood to supply proper oxygen to body tissues. thrombocytopenia causes bleeding which may be concealed inside body including hemmorhage in brain and eye retina. i would suggest to do peripheral smear to know about white blood cells( u didnt mention it in query ) . if these are also low in number then you have to meet a physician as soon as possible to come to a final diagnosis as it may be a serious problem. it has got various causes. it may be due to genetic , familial , or exposure to some chemicals etc . treatment is according to diagnosis. thanks