What Causes Tiredness,dizziness And Muscle Twitching?

hi i been having these symptoms tiredness,light headed,dizziness, unctrolable body movement within my shoulders kind of like twitching or a nervous tic, hard to focus, and as of last month i fainted twice my i can feel myself get tired the my head will feel heave then my body will collapse forward never backwards. Can You please tell me what might be wrong?