Something weird happened yesterday. I’m a bit confused, but I’ll try to convey the best I can.

For starters, let me say how my symptoms usually go. I start to notice little things for a while, like how songs seem to speak about specific aspects of my life or things that are currently happening to me. Then I have some odd coincidences, like seeing the same cars passing in front of my house. I get a bit worried about being too noisy and the neighbors thinking I do stupid things. Then, after a while of that, I get paranoid. I think a lot of stuff during these times, but I am in a stage that it makes sense to me. I sort of know that what’s happening is not right, but I end up accepting it. I usually stay like this from a few days (most commonly) to several weeks, then slowly get better.

All right, that’s how it normally goes. Now let’s get into what happened yesterday. I'll put the description in quotes so you can skip if you want.

&gt;I remember I was sitting on my computer studying. It was around 7pm. I had my headphones on, but when I was putting a different song on, I thought it’d be safer to hear things around me, so I let one ear uncovered. It was getting sort of late, and I had to eat, so I got up, went to the bathroom and fixed my hair in the mirror.  
&gt;  
&gt;I thought it was odd I was fixing my hair home alone (something I usually don’t even do when I’m going out), but I just thought sort of involuntarily “it’s because of the neighbors” and moved on. I went to the kitchen and got a glass of water, and I noticed everything seemed to be staring at me. I remembered I had to take my quetiapine, so I took it. At this moment I realized something wasn’t right. I went to the bathroom again and my head was sort of screaming “it’s happening again”. I told myself to shut up. I thought my reading glasses were hiding something important from me, something threatening or evil or whatever, so I took them off.  
&gt;  
&gt;I closed and locked all doors, including the door to my room. I looked over the window and a shadow waved through it. I thought, sort of at the same time, "someone’s looking at you” and “you’re crazy”. I told myself to shut up. At this point, I really wanted to cry but I thought I’d upset someone by doing so, so I held back. For some reason, I said “please god no” out loud, and I thought about god watching me. I told myself to shut one final time and watched some cartoons on my laptop to calm down. After watching for about 10 minutes I was feeling calmer. I looked at the time, and almost one hour and a half had passed since I stopped studying. I am not sure if I forgot what happened, or if I looked at the time wrong. Anyway, that was it.  
&gt;  
&gt;I went to sleep a few minutes after and didn’t have any other problem. I am mostly fine today.

My question is: why did it happen like that? Why did it start and stop so suddenly? I didn’t do anything different; I have been taking medication, sleeping well, and exercising a fair bit. I was doing really well. I want to think I still am.

Does something like that ever happened to anyone?

Thanks in advance.