Hi and welcome to the Chiari forum.
First, what pain meds r u taking, keep to a schedule even if it means setting ur alarm to wake up to take them, u have to keep ahead of the pain other wise it is hard to control.
Next, u need to move ur neck, there are exercises u should do to help prevent scar tissue from forming and to prevent the muscles from getting stiff and tight.( use heat for 15 mins b4 and after exercises to help loosen the muscles) Ice is for swelling.
If u scroll to the bottom of this page u will find a hyper lin to the Health Pages were we do have a list of activities to avoid with chiari and syringomyelia.Here is the direct link-
http://www.medhelp.org/health_pages/Neurological%20Disorders/Activities-to-avoid-with-Chiari-and-Syringomyelia/show/986?cid=186
For sleeping- if u have a recliner try that for the next 2 weeks, it can help with the position u r in, as it is more like a hospital bed, u were not flat....and u can not roll around.
When u do go into ur bed or if u do not have a recliner...use pillows to prop u on ur side-put one behind ur back so u can half lay on the pillow and then u r not completely on ur side if u know what I mean, but u r not laying on ur back and directly on ur scar...use the side of ur head.....this worked better for me and how the nurses in the hospital set me up in ICU and the reg room...and I did the same at home.
Post op pain can be really bad if u r not keeping up with the meds, but u said the pain is worse then b4 surgery...not sure if u mean u have symptoms that have increased or if this is surgical pain...