I keep falling asleep listening to the hypnobirthing tracks - is it still working?
Yes. Even when you are asleep the subconscious part of your brain is aware of what is going on around you, in the way that you would wake up if the phone rang or if you smelt smoke. The fact that you are relaxed enough to sleep is another sign that the CD is having a positive effect.
If you would feel more confident NOT sleeping, then listen to the CD in a place and at a time that you would not usually fall asleep e.g. after work, in the morning etc