strange ex update***

So I'm 20 now I dated this guy when I was 16 we didn't date long, but I was his first girlfriend and his first time. We broke up talked time to time then after high school we causally hooked up a few times while he was home from college. But only a few and talked once in a while but just hey how are you. He got a girlfriend so we didn't talk more which cool I get I'm not that worried about it. But then I noticed I'm blocked from all social media by him? But then over this year or two now that he's been with this girl he always adds me back on snapchat and follows me on Instagram again only for like a week or so then blocks me again? One of the times I don't even remember how long ago when he added me on snapchat he was sending me weird stuff like if I remember the last time we hooked up, and it was fun, but we are only friends. And nothing more. I said yes? I was really confused because I NEVER even slightly implied I wanted to be with him or was even flirty. It was always hey how are you from either of us, him:I'm in town let's hang out me:okay. I don't know if it's his girlfriend doing it or what, but I just think it's odd because it wasn't a serious relationship mind that it was 4 years ago, and again we only hooked up probably not even a handful of times. And again we never have said stuff like that we want to be together or even miss our relationship. So I'm quite confused why he keeps adding then blocking me. When we haven't talked in probably a year now. I don't feel I need to even ask really I can't anyways cause currently I'm blocked, it just always bothered me. Has anyone else had a weird thing similar with your ex?
Update***
I was working last night closing up, and a couple walked in and it was him and his girlfriend! I tried not to look at him and I asked if I had to wait on them(because I was suppose to be off tables just clean and go home)and my boss said yes. But said never mind they're leaving. Dodged a bullet there! Lol. Idk if they left because they thought we were closing or because they saw it was me and she got mad.