Dear Katrinm, hello.
with imbalance and heaviness in head can be due cervical spondylosis
as one of the cause.
You should do some isometric exercise
for neck muscles after cosulting an orthopedician and physiotherapist. Hot fomentation will help to relieve any muscular stiffness of the neck.
Also donot use very thick pillow while sleeping. Dont work on computer for long and while working on computer always maintain correct posture.
Pain killer along with Muscle Relaxant
will help to relieve neck stiffness. You should use medicines under medical supervision.