Shift jobs can often lead to a change in body's original biological sleep wake clock. It is possible that the odd timings are playing a havoc with your sleep.
However, every sleep related problem(insomnia) should be dealt with by an expert who will best be able to evaluate any underlying pathology for the same.
It would be advisable to seek an expert opinion to get to the bottom of this. Not only medication, certain sleep hygiene mechanisms need to be incorporated too.
Next Steps
See a qualified psychiatrist
Health Tips
Cut down on caffeine