From your description it seem as though there is a problem with the touchpad.
Here is a link to the Ifixit guide on how to remove the touchpad.
Lenovo Yoga 2 Pro Trackpad Replacement
Here is a link to the Lenovo Yoga 2 pro service manual.
If you scrol to p.61 you will find the part number for the touchpad (item #4 - 73040855).
If you search online using just the number you will get results for suppliers of the part.
Here are two examples. As you will find, the prices vary considerably. It is not a recommendation to use the sellers in the links they are shown just to give an idea of the prices. There are others that may suit your better.
Hopefully this is of some help.