You're sleeping well, just off cycle. The "secret" is to rotate forward. Take a week or two off and try rotating your sleep forward in 8 hour blocks. If you did that, you could get yourself on a more typical 11-7 sleep cycle and preserve the amount of sleep you get.

My mom struggled with this as a nurse on shifts. Alternating between 8 and 12 hour shifts as well as evening/night made it tough for her to sleep.