Hi Miss Kiani,
Stiffness of neck muscles with headache and
vomiting can be due to
Cervical Spondylitis.
It is advisable that you get yourself examined by an Orthopaedician for cervical spondylitis and Neurophysican to rule out other causes which commonly includes :-
1. Migraine
2. Cluster Headache
Please avoid sleeping on very thick pillows. Take medication only under medical supervision after getting yourself examined and investigated.
I hope this is of help to you.
Thanks.