I think I may be waking myself up from lucids.

Ok, so tonight I've had a couple lucids. One of them faded into nothing but me just laying in my bed, so I went back to sleep. The other, at around 5am, I was laying on my grandparents couch and saw a colorful sloth type thing standing in front of a porcelain statue of itself, and I did a reality check. I rubbed my hands together and moved slowly, trying not to put too much thought into it. I didn't do anything to change the dream except will the sloth away, because it was very annoying. Although, the sloth looked very sad and I felt bad, so I motioned with my head that he could follow me. Ok, point is I didn't do anything that should make the dream unstable, but towards the end, while talking to my grandpa, I wake up in my bed, wide awake and can't fall back asleep. Now my concern is this reminds me of when I was little. I would get nightmares, and I learned to wake myself up from them. I would just wake myself up, in my bed, wide awake. Sometimes when I get lucid, the dream doesn't fade away like usual, I'm just instantly wide awake in my bed. Any similar experiences? Any advice? I'm so sick of losing potential lucids.

Do you practice any stabilization techniques?

As said above, stabilization. Look at it's positive side, you can wake yourself up at any time, even if dreams aren't that long. Or you'd like long dreams without the ability to wake yourself up? Which one might be better?
I can also wake myself up, having short dreams, but with time they'll be longer and longer.

Yes, I was rubbing my hands while laying on the couch in my dream, and I waited a couple minutes to move around. Now that I'm thinking about it I stopped running m hands together while my grandpa was talking to me. But usually when my dreams destabilize, they start to fade to nothing until I'm just laying in my bed with my eyes shut. This was much more instant, and I was wide awake, almost like when I would reflexively wake myself up.

Hmm, this is just a guess but it sounds like maybe you aren't fully letting go of your physical self when entering the dream. Can you sense your heartbeat, or your breathing or anything from your physical body during these dreams that fade out? Are you using the WILD technique to induce these dreams? You might just need to find a way to anchor your mind into the dream once you get there. If rubbing your hands together isn't doing the trick, try experimenting with some other stabilization techniques. Off hand I know spinning around really fast is a good one; another thing that works well is looking at something really close up like you're zooming in on it and noticing the fine details and patterns. Let us know how it goes!

Looking at the floor for a couple seconds (no more than 3) is my best method that works for me.

Hmm... It's possible that I'm actually rubbing my hands together in real life. I punch and kick in my sleep and I've been known to sleep walk.

Sleepwalking occurs in NREM, not REM. However, it may be possible that you suffer from REM behavior disorder.