Your question is actually a common one, but let's first look at your sleep issues: Could your lack of sleep be associated with your yoga practice? Yes, possibly, but there are many many reasons why sleep can elude us: stress, diet, hormones, change of seasons, change of time zones, change of activities, job, exercise, sickness, disease, just simply aging, etc...
An all yin yoga practice is inherently as unbalanced as an all yang practice: we need balance in life. Are you nicely tired when you go to bed at night, or do you lie awake for a while? What is your evening routine: how long before going to bed do you power down an computer devices (ipad, iphones, laptops) or TVs? (Powering down one hour before bed is a good idea.) A yang practice earlier in the day will help to tire us out by bedtime, but don't do a yang practice right before going to bed: that's the time for a final mediation for the day or a short yin yoga practice.
The older we get the more we need a yin practice, but you will always need some yang too. I am now in my 60's and my preferred split is 50/50. When you are younger you can do more yang, but still do some yin. As you get older, more yin but still some yang. The yang and yin do not have to be both practiced on the same day, but it would be nice if they could be.
Experiment! Try to find out what works for your body. Once you know, please come back and share your findings with us.
Good luck!
Bernie
