I'm the same way. Some people just have biological clocks set toward nocturnal. This more than likely has nothing to do with OCD or anxiety, but there are measures you can take.
Yeah I experience some irregular sleep patterns every now and then, its just a side effect of the anxiety. Heres what you do: Do meditation in bed and force those thoughts out while relaxing your body. I have found this effective when trying to get to sleep.
This type of disorder can be caused by a lack of sleep can cause accidents, affect your relationships, and mental prowess and make you feel like you are disconnected from the world. There are treatments for most sleep disorders. Sometimes just having regular sleep habits can help.