Hi Eris. From your post I think you are probably gifted at clairvoyance and thus might gravitate more towards phasing. But I'm getting too far ahead of myself.
Can you describe the techniques you are using to get yourself in trance? I always recommend the techniques (or schedule) delineated in the MAP program- a copy of the techs are in the OBE R & D subforum, and many of the techs are stickied for further research.
The flash is known as 'third eye flash', and can be a precursor to the vision screen, but not always. We call the expanding blackness a few terms: 3D Black, the Void, and sometimes just 'space', and is a precursor to either phasing or OBE, but in the beginning..
This is also not unheard of, and it's why I recommend you change your practice time to early in the morning. I know it sounds terrible, but if you get up two hours before 'regular' wakeup time, stay in bed and then practice, you get to deep trance easier (you skip all the relaxation time necessary to get to the threshold of trance) and if you fail, you just fall asleep for the prescribed time, but more importantly, it doesn't mess with your sleep cycle, and avoids setting you up for all this waking up. Unfortunately, OBE practice disrupts your cycles, because most people have delta sleep in the last part of the first cycle, and all of this gets messed up when you are trying to stay aware as you fall asleep- it can cause an alpha intrusion and train you to 'not sleep' when it's time to sleep. I personally practice on a recliner (very comfy recliner) that I have set up in my bedroom and don't practice every day- I practice on and off throughout the week and try a projection on the weekend, to avoid the sleep cycle mess up. The good news is that when you get used to a routine the fatigue and sleep messup does resolve.