When i lift my arms up over my head and arch my back to stretch, i get a shooting sharp pain through my lower abdomen. what could cause sharp pain?

Spine problem: You may be compressing a nerve root in your spine when you arch your back in the manner you describe. You should see a neurologist who may need to order an MRI or ct scan to see why this happens: disc disease, tumor, bone growth, etc. Until you are seen and evaluated, try not to stretch in that manner, and do not see a chiropracter.