Sleep what's that?

For the past month or so I have been unable to sleep at night. I seem to be reverting to my old ways or at least my body wants to. I worked nights for 10 years but for the last 4 years I have been on day shifts. The first year after the switch was hard but I adjusted. I always found it easier to be up at night I am a night person and always will be but I adjusted and I thought adjusted well. For the last little while just can't seem to sleep at night I don't even feel tired at night but all day its a struggle to stay awake. As the sun set I start to wake up and feel energized. This is making my life hard at the moment because as I said I am now on day shifts. Last night I did not even start to feel tired until 5am and I normally get up at 6:30am so right now I am so tired I fell sick but tonight it will be the same thing around 6pm or 7pm I will suddenly wake up and be good to go for the night its getting frustrating.