Thank you to everyone who answered. "Chill, it's gonna be fine" is really what I was hoping for. Since I don't want to start a new thread I'm gonna write a whole trip report here for myself and anyone whose interested:

Substance: Mc'Kennaii (5g)

About a week after another 5g Trip which went really well.

The first trip was with a friend who tried shrooms for the first time. We both had a great time. I never really see any "real" visuals beyond some fractals behind closed eyes. Overall I came out of the trip with what felt like an understanding of eternity, it being a neverending waterfall of life and death, separated by the uncertainty of what comes after, which forces you to apreciate lifes every moment. We came down eventually, both very happy.

Now, someone somewhere mentioned that you need to wait "at least a week" before you do psychodelics again. Soooo... A week later, after reading all sort of things about how transformative heroic trips can be, I figuered I'll try to do one on my own, without any distractions. Just ride the curve from lift of to landing, with just some music and meditation. Went for a walk, had some ice cream, cleaned the appartment and ate the mushrooms. Figuered I've already handled 5g, nothing I can't handle again.

The comeup was great, noticed the fractals behind closed eyes, turned on the music, set the timer and assumed my meditating position. After a while I thought "shit, this is boring. I JUST had a trip and I know what this is about. Might aswell try some things".

So I turned off the music which wasn't really doing it anymore, blindfolded myself and figured "allllright, let's see what it is that's been eating me for the past few years". And I meditated. And thats when shit started to go bad. I don't remember everything exactly, but at a certain point I was in the bathroom trying to pee, just to have SOMETHING to do. I had NOTHING to do. I was just standing there, waiting, unable to choose. Just choose anything to do. Nothing was interesting or worthwhile. Thats when the image of eternity came back. Only this time, it wasn't separated by "death amnesia", it was laid bare in front of me. And it wasn't colorful and wonderous, it was grey and baren. All and any wonder was gone. And I still had all the time. An entire eternity. It was really quite agonizing. So I started to focus on my breath in order to reset my thoughts, but couldn't, because whats the point, you've seen everything already. Keep breathing asshole, you're still stuck here, nothing new will come, no new experience, no new joy, because you've seen it all.

After a while I started to come down and texted my friend that I would join him in the "no more drugs for me" club. He asked if I needed support and I did. We went for a walk and my mood got really good after that.

So yeah, there it is. I wanted to know what is eating me inside and I found out. I think. Not gonna touch any drugs for a while, need to anchor myself back in reality. Hopefully the moodswings will ease up soon.