How can I fix my sleeping pattern?

I would recommend trying to get some sleep using a sleep aid. Whether its warm milk or tea to throwing you blanket into the dryer to get it nice and warm. Try the stuff that might bore you like reading a book or watching a boring movie. Soap operas if your a guy cspan if your a girl. Try to set an alarm that will wake you up at a certain time and keep to that schedule. Don;t take sleeping pills or any medication unless your doctor tells you to.

I can suggest that you try and just relax on a day where you don't have to do anything, sit in front of the TV and just have some coffee, don't have coffee after 5pm though. You can try to go to bed at around 7-8pm if you're really that tired. Try and stay up until then, keep yourself occupied, go out for a walk in nice fresh air. It should wake up a bit. You could also try cold water when you start feeling drowsy. If the problem continues, I recommend seeing your doctor. Hope this helps!

http://lifehacker.com/5548150/how-to-reboot-your-sleep-cycle-and-get-the-rest-you-deserve

I feel you.

My sleep schedule was sleep at 10am, and wake up at about 6.
You need to first find a way back to what you consider a regular time. I slowly, every day, would go to bed an hour or two later than I did the night before until I found a reasonable time.
Once you're able to get to that time, make sure you're doing constructive things before bed. Close the laptop, step away from the tv, and put down the phone. I suggest a bath, or reading, even if only for a half hour. It works your brain out, gets you away from the bright flashing lights, and can be very relaxing.

Fast for 16 hours until the next morning when you eat a solid breakfast containing protein. Fasting has been shown to reset the inner clock, and breaking the fast when you are supposed to wake will decide your new daily pattern.