Sore back of neck, excruciating pain in the back of neck if i move it up so cannot have weight i the front of neck, right leg giving way now 2 days?

Seek medical review: Without asking quite a few more questions it is difficult to be clear on the cause. Neck pain + leg weakness is a concern and you should consider seeing a Dr for a review. Have you had an accident or did this occur spontaneously?

The addition of: Right leg weakness " giving way" to severe neck pain, could indicate pressure on spinal cord. This should be treated immediately by consulting a Neurosurgeon or Orthopedic Spine Specialist. Get help from Primary Care doc to set this up fast. Other warning signs include worsening arm or leg weakness, incontinence of either kind. If not treated rapidly, damage can be irreversible.