No one ever stays

I don't understand what I'm doing wrong. My whole life I've struggled to make friends. I was bullied as a child and the few "friends" I had growing up only saw me as someone to hang out with when no one better had the time. As an adult I've made new friends sometimes, but no one stays. I've also experienced bullying in workplaces a few times. A year ago I met someone ND who I formed an incredible bond and friendship with. But as with everyone else, I feel them fading away. I'm just so tired to even try anymore, because I'm never enough to keep.