I dated/hung out with this guy for like a month over half a year ago. He ended it because he just happened to live 4 hours away and did not want to put the effort in. He, in general, was not the type to commit and would always go to whatever is the better option for him (whether it is me or his friends). He would sometimes ditch me to hang out with them. Right before he left school for the semester, I told him I did not want to talk to him all summer because it was too mentally exhausting. He respected that, but it only lasted a month. We both confessed we missed one another and talked more over the summer. I ended up dating someone new during that time.
As the school year arrived, he started talking to me less. Whenever I would see him on campus, he would say he wanted to see me, but when the time came, he acted as if we never talked about it, go hang out with his friends, and he was not even happy to see me. By the time the semester arrived, we stopped talking.
We are in the same student (how we met) and now in the same job as teacher assistants for a class for freshmen. During this semester, I would only see him every week at meeting but we would not even acknowledge one another and I even lost my friends I met through him, which I know is quite normal to occur.
This past week, for our job, we have to go to biweekly meetings and I had to go to his. I said hi when I saw him but our conversation doesn't last long or anything. He wrote a tweet saying that it is weird going to a work meeting with his ex and should not date a co-worker again.
When I saw that, I was thinking he should not even worry about it since it was so long ago and we did not even date very long. He is not very experienced and has never had a girlfriend before either. I do not even consider him my ex!
Why is he still taking this seriously or why does he think it's weird being around me even if we see each other every week and we have not even talked?