I have two issues; I seem to have lost enjoyment for everything and can't love anyone.

When I was a kid, it was extremely easy to appreciate simple things, and each day had something fun for me. I used to be crazy about everything in nature and would read books about animals for hours.
I also felt a very strong emotional attachment to my parents and the thought of them dying would get me wailing like crazy. I really liked my parents. I also made friends easily.
When it came to fictional stories, I would often develop strong emotional attachments to the characters, as if they were real people.

Nowadays, I get bored and frustrated easily, and the only thing that truly makes me happy is eating (pretty sure that's because of an eating disorder in the past.). Nearly every day, I feel dead. Animals and plants are no longer interesting to me.
I recall that as a kid, I could read novels for hours. However, when I pick up a novel now, my attention span can't last for more than five minutes. It's crazy. I've read through at least 5 novels in the past few months, but I never really got actual enjoyment from them. I even picked the novels with good ratings and seemingly compelling plots. After reading, I never remember any details. It strikes me how others can be huge fans of a book and feel very emotional about them, like when a character dies. But I never even seem to care if something awful happens to a character.
I've tried various different hobbies such as violin, trumpet, reading about other fields of science, art, ceramics, and nearly every sport in my area, but I could never last in any of them for long.

Also, my relationships have been badly affected too. For example, ever since I was a teenager, I stopped wanting to make friends. Talking to people became an enormous chore. I think it was partially due to some social anxiety. I don't know the exact reason why I hated talking to people, but it just felt like a huge chore to stay around them. Maybe the judgementalness from everyone subconsciously repelled me away from opening myself up, because the expectations for teenagers were quite different from expectations for children.
I basically stopped caring about my family as well. Maybe it was because we got into fights too much. But even after being separated from them for about a year, I still feel as if I don't really care about them. It's like I can't forgive them or anything. It feels emotionally numb.
Ever since I was a teenager, the only emotions I could feel were irritability, sadness, and anger. When happiness did occur, it always lasted very shortly, and never even felt like real happiness. Nowadays, eating is the only thing that makes me happy.
I made some new friends recently, but I didn't put any effort into befriending them. They just stuck around me. I know that I'm quite lucky to meet such friendly people, but I feel like if they rejected me or just abandoned me one day, then I wouldn't miss them. It's very scary to know that I wouldn't care if someone just left my life.
As a teenager, I also recall feeling rejected and lonely all the time, but I'm not sure if that has to do with anything. As a kid, there was always a sense of security, like my parents would always love me. But after we got into so many fights, I don't think that's true anymore. All the stories about friends leaving each other or awful divorces don't help either. When I'm around people, it constantly feels like walking on eggshells, like I can be rejected and thrown away at any moment. I'm guessing this is why I can't form emotional attachments to people.
Perhaps teenage hormones are still lingering on me. I don't know.

I'm not sure if rejection and the things that happened to me in the past have shaped the emotional numbness.
I don't know how to enjoy anything or anyone anymore, and I would like to know how, if possible.