my docotor prescribed me 0.25 xanax to take twice daily as needed. i started off takin only half in the morning and half at night. it worked for awhile then it quit ( I guess my body was gettin use to it) so i started takin a whole one in the morning and a whole one at night. I have been doin this for about 2 weeks and its startin to make me feel VERY jittry at first and VERY dizzy, after about two hours I start feeling a little better. Do I still need to be taking it or do I need to tell my doctor and quit?