It's a bitter pill to swallow, but the truth is that some people just aren't meant to be loved. I think accepting that is, for some people, a bit part of growing up and becoming a more mature person. You gotta stop being envious of others who possess something you never will and just kinda...get on with your life. Find a cause you care about. Put your energy elsewhere. Maybe stop watching romcom anime.
I don't know if that's a part of the problem or just a separate problem altogether. We expect people to partner up, when we should normalize people being alone. When people don't or can't, we might be hardwired in our monkey brains to see them as outcasts from the group.
That's pretty much where I'm at. I'm 38 and supremely pathetic in the eyes of society. I've just accepted that I'm entirely undesirable and live how I want to, or at least live in the way I'm allowed to. In a way I've turned into my parents where I find myself saying "life isn't a fairy tale" to people kinda often lol there is no "someone for everyone."
I'm not completely discounting the possibility you're right, it is possible you're just very unlucky, but your line of thinking is pretty consistent with people suffering from depression, and depression tends to make you make decisions that make you stay depressed.
Not for quite as long, but I've been there my friend.
I don't know how to tell you how to alleviate depression, but I can say that if you manage to, things may look drastically more hopeful afterwards. When you're really truly depressed, the idea that things can get better just doesn't make sense. You can't trust your ability to judge that though because when you're depressed the part of your brain you need for that just isn't working right. It's not capable of telling you whether normal happiness is possible, you no longer have the tools you need to judge things accurately.
If you're like I was, your depression also tells you that you are special in that the ideas that work for a lot of people who go down a path of trying to get better just wouldn't work for you and it will take any minor setbacks as proof of the same. Your depression isn't exactly lying to you, it's just stupid and it's not qualified to determine that.