I guess social media can often depict a happy lifestyle, without any hardships. Most people post happy times and out with their friends often. I think this distorts reality.
As you say you are good natured, kind hearted. My suggestion would be to start small branch out to one friend, even if it is rekindling with your primary school friend.
Then pick up some hobbies along the way sport, dancing, perhaps the gym and start small "hello" little conversations.
Hope this helps
I've come to classify relationships into three categories:
Destructive - relationships that actively diminish your quality of life or that make you lesser of a person
Stagnant - relationships that are comfortable but that do not push you to explore yourself or the world around you
Constructive - relationships that actively invest in your wellbeing and future, that encourage you to be better
Both destructive and stagnant relationships detract from your capacity to be the best person you can be. I've come to realize that the vast majority of relationships I have had in my life, particularly when I was younger, we're stagnant. People that I would hang out with because we shared similar interests or had similar humor. We'd hang out, play video games and talk shit. But there was never anything really anymore than that. It was comfortable but empty. Would my life be any better or worse without these people in my life? Not so much. It wasn't until much later on that I had my first constructive relationship and it opened my world up. It was like having someone pull me out of a dark hole and into the sunlight. Sadly I myself suffer from severe anxiety and depression and I think that my problems have wound up pushing that person away, but it goes to show that those types of relationships can and do exist.
I think for people like us those sorts of bonds can be derived from people who suffer or have suffered from similar issues. Shared experience and prolonged support and understanding could breed constructive relationships. Though I suppose the opposite could be applicable as two people suffering from depression may wind up relying on each other as a source of personal happiness which is a terrible burden to wear.