Be a better friend

I am having some problems. I am hoping that putting them out here will help me to better understand them. I am trying to figure out why I have such a hard time making and keeping friends. I know how to be a good friend. I listen, I talk, I offer support, I make myself available to others. At first I am shy, but I always have a smile and a hello for people. I’m just not sure if it’s me or everyone else. The friends I do make are usually safe or completely toxic for me. The ones I do want to make I feel like I just can’t connect with them. At school I feel like the outsider. I try to go talk to them, I smile, I am friendly, but I just can’t get in. If I am standing alone, they don’t come up to me and say hi and start conversation…they stand alone and wait until one of their “Clan” gets there. Even If I smaile and say hi. I just don’t get it. I have been hurt in the past and I know I have trust issues. I have tried to knock down those walls. I just don’t know what to do. I am so lonely. I want to be accepted, I want to have a friend I can turn to and vice-versa. What am I doing wrong? Why don’t I fit in? I’m like everyone else. Is it just my insecurity? Should I just give up and accept life the way it is? It seems even harder as an adult to make friends. Why is that? I have never really had a Best Friend…not a true one. The few times I thought I had one, turns out they were using me, stabbing me in the back or just “grew out” of me. Does anyone have any advice? What can I do to make myself an easier person to be friends with. I can’t think of nything I haven’t tried. But I’m all ears at this point. I can’t get any lonlier, or can I?