why my back pain aggrevates while exercise

Do you use a lumbar support belt??

Hi Deena,
I am not sure where you are going wrong, but take care of few points and see whether your back pain aggravates or not:
* Are you doing right exercises ? There are some exercises which are strictly prohibited or contraindicated for those having back pain. There are some exercises which need to be modified in order to prevent back pain.
* If you are doing weight training, see to it you are not lifting too heavy load.
* Learn proper lifting techniques and take care of all ergonomic measures.
* As Vasanth said, use a lumbar support belt if you are doing intense weight training.
* Never hold your breath while doing any exercises especially weight training as it leads to increase in internal pressure which can cause severe back injuries.

Take care of these few points, hope it helps.