I don't like where I am in life anymore.
I'm 25 at the moment and you've so accurately described the last few years of my life.
Where I used to jump at the opportunity to go hang out with friends for fear of missing out, I now just prefer to do my own thing. It's not a bad thing, but it can be really weird and it can feel like something's wrong.
All I'd say is that we change as people.
Think of all the foods you used to hate as a child - do you still hate all of them? What about the ones you used to love - how do those taste now?
I know food and lifestyle are two very different things, but how change affects us is pretty similar. We've all had that experience of doing something again, or going somewhere again, after years away. It doesn't have the same magic as it used to, and it's pretty disappointing.
So I'd say definitely keep trying to find who you are. It's really rewarding but it's also really tough, so don't be afraid to talk to people about how you're struggling with that. We're here to listen, and it sounds like your partner's friends would be really supportive and understanding as well. It's okay to be distressed right now. You're lost, but you're also trying to find yourself again.
It does sound like you've 'grown out of it'. If it does make life easier and isn't harmful, it does sound like it's a good thing for you.
A lot of change at one time can be scary and unpleasant. If you are struggling with this, a lot of people go see a counsellor or even their GP to have a chat about how they're going. You haven't said you suspect depression or anxiety, but even stress is often a reason to go have a chat to someone.
Just something to think about. It's an option you can take if you like.
Hope things are going a bit better for you.