I'll go at it "chronologically". I'm quite worried about it.
- Yesterday: I wake up with a serious headache at around 5-6 AM. I sleep back, only to find out it's stronger at 10 AM.
During the day: It's so strong. I thought it was already very strong as the top of my head was sending pain signals, but as I sneezed, it was so intense that I took myself to sleep at 6:30 PM.
No serious neck pain at all. Probably very little.
Details on sleeping: I covered myself with a blanket I'd use on spring (or maybe winter), since I somewhat felt cold.
Maybe independently from that, I had a diarrhea some time after waking up.
- Today: Woke up around 5:10 AM, headache was not as intense. However, I somewhat felt my neck's right side was a bit puzzling me. Nothing intense. I thought it was just me not sleeping correctly. I drank some coffee and it seemed to ease the head pain. Regardless, the cold feeling was "exterminated".
Throughout the day, though, it intensified - somewhat making it feel rigid. Left side is now starting to "itch".
To top it off, whenever I move my eyes upwards, downwards, left or right, they hurt at the direction I move them at.
All in all: Yikes. Worrisome since I never experienced anything like this.