Reading, soccer, cartoons (Adventure Time, She-Ra and the Princesses of Power, Steven Universe, The Owl House, South Park, etc.), Doctor Who - the new series before Chibnall, PC games.
I know how that feels too. Sometimes I think that I'll never be happier than I was in my preteen years. But life goes on, time heals, and most importantly - without sadness you can't know the real value of happiness.
I guess that's true. I have my boyfriend in my life, which I'm more than grateful for, but I'm genuinely unhappy in other aspects, like with my job and my relationship with my mom and I wish I could be with him so I can get away from all this bullshit.
You are still lucky to have all this - a significant other, a job. Many people only dream about that. I hope things get better for you, but it's only up to you to overcome the obstacles. Just don't dwell on your sadness for too long - try to find a way to deal with it.