Astral Block and Nightmarish Lucid Dreams

Hey guys. I'm new here and no matter how many times I've tried, I've never been able to astral project. I either fall asleep, or start feeling strong vibrations, get excited and then they're gone and I can't get the feeling again. I lucid dream a lot, but strangely, I can't control my lucid dreams and a lot of times, they end up being nightmares. If you have any advice on what I should do, or how to deal with this, I would greatly appreciate it  :)