I tried a relaxation technique lying on my back… Well spent there over one hour and nothing. Then I figured out that anything can’t be done in that position as I can’t fall asleep at all.
But if I try to lie on my side, I fall asleep nearly instantly with my visualizations and it’s game over… Is there any way to stay conscious while visualizing and NOT to black out totally?
There isn’t much that can be said about that, really. The more you practice, the longer you’ll be able to consciously witness yourself falling asleep. I too sleep on my side, and had always tried to WILD on my back until I read a post about someone who could do it on their side. I need to get unused to thinking ‘laying on side = sleep’.
It gets much easier after a few hours of sleep. I successfuly WILDed twice on my back and once and a half time on my side. All you need is time.
So you mean WBTB. Yeah that is indeed a great way of WILD-ing. Just 5, 6 hours or so. 
Astralicious maybe you could try sleeping on the opposite side to the one you usually do (if you sleep on one side specifically.) Perhaps that will help mark out in your mind that things are different, but not prevent you falling asleep.
Try counting your breathing (inhale 1, exhale 2, inhale 3, exhale 4, etc.) might work.
I love the FILD/HILD-method. This method is easy, and you are allways aware (unless you do something wrong)
I got my second LD because of that. (I mixed it with WBTB)
But you can only do it more easily if you are very, very tired. So I suggest you to do something like counting breathings indeed, Astralicious.
wow i have the EXACT same problem. weird. Do you ever get the sensation while on your back that you are exhausted? Like you have to turn onto your side or else bad will happen.