Last night I had a FA: I woke up normally and realized it was too dark outside, so I checked out a clock and thought: “This is very odd, I must be dreaming”. Then I performed a RC by pretending to fly; instantly I felt shivers, random vibrations and ended up trapped in my bedroom walls. Eventually I woke up like if I had woken up from a nightmare.
Last time I became lucid it wasn’t that scary, I just jumped a 30-feet tree 
and thought: “You can’t jump that, can you? You are dreaming!” but then I just jumped another huge tree to check out my dream jumping skills and instantly woke up.
Well, I just can’t mantain lucidity more than 2 seconds and that’s pretty frustrating. I’ve read some tips on that but I don’t even have the time to think about that when I become lucid! It feels just like I will wake up no matter what I do or think. Any idea? 
If you think you will wake up instantly, then you will! Try to be positive…perhaps you should try chanting “I am dreaming” at first and stay still. This reminds me of one of my LD’s when i was worried that i would start to feel my body and destroy my lucidity. Once i started thinking of it, It happened! Good luck!
Stuck in your bedroom walls? I can’t I’ve experienced that but I’ve always had the feeling of being stuck on many occasion when I experienced sleep paralysis. Usually I just kind of will myself into another dream. As far as staying lucid I would go to the “Stay lucid” section on the webpage under the “while” menu, it has some great techniques, including one I’ve often used. Simply make yourself spin in circles you’ll start feeling slightly dizzy, this leads to false awakenings of course but I prevent that too. If you feel like you’re going to have a false awakening, or simply don’t want to lose lucidity just remind yourself “I’m still dreaming, I’m still dreaming” this has worked for me in the few lucid dreams I’ve had…usually I have the false awakening but I stay lucid anyway…
Or just rub your hands.
I had once simmilar experience: i had LD but i felt that i will wake up. I knew that most times when i feel like that i am close to FA. After waking up i did RC, got lucid, but i was still lying in bed. When i wanted to get up, i falled a bit, an i was unable to move. I got stuck in bed. Like a paralysis.