Oh, man. Where do I even start.
First time I remember it happening would be in high-school. One night I had a "nightmarish" sensation where I could see a creature in front of me, just staring at me while my heart was racing as I was feeling like the creature was silently threatening to harm me. I'm not sure how long this lasted, what I remember is slowly regaining the control of my body, the hallucination slowly fading away as I finally started feeling awake. Now, I'll just start by saying I'm usually the biggest skeptic in the room, but I was interested and couldn't let the sensation go. Generally we would skip a class or two in high-school due to our homeroom teacher being very forgiving in terms of our juvenile behavior. I discussed this thoroughly with couple of friends during our "break" and we would spend next few days talking just about dreams and stuff. I remember running into an article somewhere few days later, about trying to force sleep paralysis.
I tried it out and to my surprise it worked, first try. This time it started by me being fully aware of what was about to happen, I remember how it manifested as a sensation of fear and paranoia. I couldn't move anymore, I was somewhere between being awake and dreaming. My thoughts started to jumble and I started to see a figure forming out of what usually would be my desk chair. The blinking light from my PC was suddenly glowing very bright, and all I could stupidly think of in that moment was "ALIENS ARE HERE TO TAKE ME". I couldn't move at all, I remember trying really hard, to no avail. I was slowly getting drenched in sweat, and after a while the hallucinations faded away, giving form back to my chair. I was very startled by the experience, so I put off scaring myself ****less for the time being.
And then it happened again, way worse than ever. This was around 4 years ago when I returned home after a very tiring day. Spent a whole summer day out without sleeping the previous night, I instantly crashed the moment I got home. I remember the breeze coming from the window was very soothing, my focused thoughts about it keeping me from falling asleep. And then the usual sensation of fear kicked in. This time I was directed to the wall next to my bed and I couldn't see anything else. The lights slowly started fading away as dusk was approaching and I could feel something slowly creeping in from my feet up to my face. The creature was next to my ears but I couldn't move a muscle. My heart was racing and all I could think of was "okay this is the end, I'm going to die, I hope he just eats my head quickly", but the creature just kept looming behind my back, cussing at me and creeping from every angle. I started feeling the pressure slowly pressing me to the bed from above and I felt like I was at the very edge of the bed, just about to fall off. This persisted for who knows how long and like usually I slowly started regaining consciousness and control of my body. But this time it was different. One of those sudden summer storms started and I was still terrified and panicking, scared about the creature. The sudden change in atmosphere definitely didn't help my emotions. Even though I was starting to feel fully awake, the paranoia persisted. I was too afraid to get out of my bed, even more afraid to leave my room for good 5 minutes due to my belief of this creature still roaming around, until finally coming to my rational senses. That's the first time I legit felt paralyzed and unable to do anything but race against my thoughts, while fully awake.
Luckily I don't recall similar things happening ever since. There's a nightmare every now and then but nothing this vividly close to an experience akin reality.