Wel come to HCM
Your history suggests you have spine related pain may be associated with muscle spasm,wrong posture can be one of the cause, but it may be something else also so do not ignore it.
You should consult orthopaedic surgeon
.after examination a simple X ray
of spine and some blood test
are helpful o know the cause.
A MRI Spine can give very useful information about the cause do it after consulting orthopaedic surgeon.
In the mean time a simple analgesic
and local hot fomentation will give some relif.
Please do not use high pillow,and sit in correct posture.
Once your pain is gone do regular exercises may be better explained by phyiotherapist.
Good luck to you