I tried FILD a year ago which didn't work. I recently got back to lucid dreaming and strange things happened.
First of all, I had a notification play on my phone at a specific time at night(I slept at 11, so it played at 5:00) when i woke up, I couldn't remember a single dream (and I usually remember at least 2-3) but that doesn't really matter that much. I woke up and the first thing that came to my mind was FILD, so without opening my eyes, i started to slightly tap my fingers. The way my hands where placed, they where on my stomach. I didn't wanna move them to my bed because well... i didn't want to move xD. So as I started doing that I noticed my heartbeat going up, really intensely. It was like running a marathon. My breathing didn't speed up though. I tried to calm my self down, but i started feeling REALLY anxious, and the heartbeat got worse. At this point I panicked and quickly moved in order to snap out of it, but I could still feel my heart beat. It slowly faded away.

What do you guys think it was?

I read around a bit, and it seems other people experienced something like this with WILD. I read that it was a hallucination, and i did actually hear it more intenesely and echoing through my head, but I it since I could hear it after I rose from bed for a bit. Also, it felt REAL. It didnt feel like i was sleepy or about to fall asleep or anything. Then again, i never experienced sleep paralysis or other hallucinations. I didn't enter SP. or at least I think I didn't.

Also, why did i start feeling anxious? Is that normal?

I guess tonight I'll wear my fitbit to bed. It can record your heartbeat during the night (and apparently when your heartbeat rises, you are dreaming), so if that happens again I'll find out if it is a hallucination

Thanks!