Interrupted sleep even after taking meds

I have delayed sleep phase disorder(Usually falling sleeping between 6am-8am). Since the last 8 days I have been taking zolfresh 10 (zolpidem) just before going to bed at 10:30 pm. Surprisingly I am able to fall asleep in 30-40 min of going to bed. But I wake up 1.5-2 hrs after falling asleep then after 1-3 hrs of being awake I am able to fall asleep again..but then again after 1.5-2 hrs I wake for somewhere around 1-3 hrs and fall back asleep. Some days I am able to sleep for 5 hrs(actual sleep) and some days I sleep for 13 hrs(actual sleep). So basically zolfresh helps me fall asleep quickly and in the night but I keep waking up every 2 hrs. How can I have continuous uninterrupted deep sleep?Also some sleep hygiene suggestions would be helpful.