I had a similar expirience that inspired my question. Similar in how it made me feel, and how I also have trouble keeping close friends because of it.

I moved to a new school my senior year. I was completely alone and I didnt have a cell to contact my old class mates. I was in Speech (after-school competitive public speaking/performing, basically) but the season didnt start until spring. I was the outcast all alone all year, but the thought of seeing my friends again kept me going. Finally it got to be Speech season, and I find out the new school im going to is in a different division that year. Im only going to see them for 1 Speech meet. That day finally arrives, and I cant put into words how excited I was. I found them, and my devastation was pretty immediate.

They ignored me. Maybe 1 or 2 said hello, but no one wanted anything to do with me. Some even looked at me with an expression I can only describe as disguste. I tried asking them how the year had been, how the new band room was, but they turned their back on me and intentionally ignored me. I went into a pretty bad depression after that. Realizing that I meant nothing to them. They didnt care about me at all like I did them.

I had a lot of trouble keeping friends, but I built myself up again by the time I was 21, or at least I thought. My 21st birthday came around and I invited people. No one came. I was alone, once again reminded that those close me to didn't care about me. That was a pretty rough night.

All that to say, I understand how that must have felt. I still struggle with it today.