So how do i explain this (especially because english is not my first language, so sorry for any mistakes in advance)...

Welp lets jump into it.... Even at my early childhood days it felt this way: if I did not do most of the "work" in friendships, no one will engage with me. Like i had to literally chase people for attention and affection. I don't know if this is a *result* of my mental problems already back then, or if this is a *cause* to developing them. 

Let me give one example:

I text (old school sms) a friend some casual stuff "how its going, wanna do something next week" - he answers "yes" - and then: nothing happens. I have to either keep spamming him with requests, or be physically with him and ask to do something *right now*. I barely got rejection straight at my face - but i somehow always just got forgotten when things were planned in advance. Also no one visited me at home unless i invited them, and then half of the people would pass or not show up. No one ever invited ME unless i was "accidentally" in class when a "friend" invited other people to his birthday party or whatever. One could say: I had to 100% invest all the time and effort for friendships, otherwise they would just die out. It was just... weird. Barely anyone would openly reject me, but no one would actively seek my companionship. Like "lets play the friend when he is around, but when he is gone lets just forget about his existence completely".

This is even true for almost all family members. Like what is this even? I can understand if a romantic interest gets turned off my my clingy behavior or sometimes even obsession. But just basic, casual stuff towards friends, including just casual friends? Iam not talking about not getting an answer within 10 minutes. Hey i was a 90s kid, we didn't even had this whole chatting stuff with "marked as read"-checkboxes back then. Iam very sure i wasn't clingy at all within friendships, especially since, again, there weren't even as many technical ways to be clingy back then. I also never called too frequently or did anything else one could have seen as "forcing myself onto others".

No, all i was expecting was like 50/50 investment in friendships.
Which, oh who would have though, was the case with almost all other friendships i've seen.

It really felt like people would intentionally keep me at distance and only engaged with me when they felt they *had to*. When it comes to romantic relationships i know my issues and flaws, especially my early day out-of-this-world expectations. But friendships? Is expecting 50/50 effort investment really such a high standard?

The biggest irony... and i mean next level bad joke irony... happens when nowadays old friends or family members ask me stuff like "Why did you play so many video games as child instead of going out?". Like what the f was i supposed to do? I was as the only kid in the neighborhood. All "friends" kept me on some magical distance that somehow only applied to me. 

Am i the only one who experienced this? Was i the problem even way back then? Bad luck in finding genuine friends that may could have mentally stabilize me? Or was this always just a classic case of being overly sensitive?

(This whole topic just came back into my mind since it just happened again with a cousin some weeks ago.)