Do I need a Chinese Visa?？？

Here is my itinerary, May 3 leaving Taiwan arrive in Hong Kong, May 6 Leaving Hong Kong arrive in Chongqing, China at 2:45pm and Leaving Chongqing at 12:45pm to Taipei, Taiwan. Do I qualify for 72 hrs exemption ? And I have a US passport will travel from US to Taiwan in April and leave Taiwan for US May 23