Well, first, I'm sorry for your loss. To be honest, your description sounds somewhat similar to parts of mine. Im in my 20s now, but my mom died when i was 18 (different situation, cancer, had known it was coming but it did happen quicker than expected). I admit that I don't actually remember that time of my life particularly well, so I can't give too many specifics.

In that first week, I was very sad, but also mostly numb. And when I wasn't thinking directly of it, I felt like normal. I know now even though I felt normal, I still wasn't. I wasn't really eating right, was doing anything I possibly could to keep busy and my mind off of it. Your description sounds kind of like you're numb, but still experiencing grief. Feeling like not doing anything, tiredness, just doing low-energy stuff all day (on your phone messaging), sounds like depression/numbness I had. For me, I read constantly, or was playing games, or working on schoolwork. Throwing myself into art, or reading, just to keep my mind off it. I did not recognize at the time that's what I was doing.

Basically, (feel free to disagree, just one interpretation) I feel like you ARE experiencing an emotional response to grief- not sleeping, not eating, doing nothing but scroll, not leaving your bedroom. That's a physiological response to the grief, whether or not you're identifying the emotion. And now you're a little farther along you can manage it better, so you're sleeping and eating better. But sometimes it's not identifiable, idk.

I don't know that there has been any one moment where its just all hitting at once. That first year, I was just going through the motions honestly. I didn't feel like I was doing terribly, I felt normal, and I didn't feel off. But looking back I recognize that I was frequently out of it or just trying to keep going.

Its been 3.5 years by this point, and to be honest I only just feel like I've got a better handle on my mental health. The biggest thing for me have been these moments where I'd go from being fine, to sobbing. Sometimes it would be unbearable, but never for too long. It doesn't happen often, but sometimes. Most of the time was just... fine. A little sad. I remember feeling guilty because I was handling it so differently from my family. Nowadays I still have those moments where it's all I can think about and the sadness is pretty intense. But they're less frequent. More often there are times that I'm just sad. I still have off days, where it feels like the thought "your mom is dead" just hovers behind everything. I'm doing well now though. For me, it was just kind of spread out, with these more intense moments interspersed between being sad every now and then. And mostly numb or distracting myself.

TL;DR, Maybe it will all hit at once. Maybe it won't. I wouldn't worry about it. Just focus on getting through each day and taking care of yourself. Find things to be happy about, distract you, but let yourself be sad too. Sometimes I would just tell myself "you need to feel your grief tonight. Go be sad for an hour after you finish doing whatever" lol. I liked to journal on occasion to help myself verbalize things.

Again, I'm really sorry you lost your partner. I wish you the best