Hello traveler :)
Do you travel only at night? I found that when I travel at night it is nearly always dark in astral. Traveling at the daytime produces nearly always daytime in astral.
Now, you should not feel to be scared. Train balance and unattached observer attitude.
I ave the same experience as yourself, dark surrounding, but I was advised in astral by probably my subconscious self that :
There is light. You have to learn to see it Everything shines with weak inner light, you only need to find way to see it. I also found, that I produce very strong aura, which I can extend to large volume... to even 50+ meter in diameter. It can be used as light source, but it functions also as passive weapon against everything. It is possible to manipulate it... its strength, its shape... I didn't manage to manipulate its colour ... yet.
I don't write many of my experiences in DJ, only if they were interesting for me. Here is a few experiences with darkness:
Serial Out of Body Experiences - Dream Journals - Lucid Dreaming - Dream Views