I think the problem lies right in the very first sentence: 'Whenever a guy has really liked me, I have never gotten "that feeling".'
I think you need to find a guy that you like, regardless if he likes you or not. The way you describe it, seems like you're just trying to correspond to their feelings with feelings that you have to fabricate.
From my point of view, perhaps the reason that by the time you get “that feeling” and they don’t for you, is maybe because of the length of time it is taking you to reach that point and by the time you do, the emotional connection you now have with him---he no longer as the ‘feeling’ because of that length of time. Relationships take work and you have to nurture those feelings between the two of you and maybe while you’re figuring out how you feel, about the one you’re with, he’s falling out from those feelings because they haven’t been nurtured as they need to be. That could be part of the problem with why they don’t feel as much for you as you do for them. You might consider reflecting on what your thought process is when you are with someone and the process your mind and heart go through when you're figuring out just how you feel about someone.
Well odds are your mixing up sines or picking guys that have general interest in you from a physical and or sexual prospective rather that an actual like and want to get to know you prospective. But that's just a generalization and a simple assumption on my part. Do you have an example of both cases so I can better understand where the issue is. Like what's an example of a time where you kind of liked someone and they didn't like you the same way and one where they did like you but you were unsure?
Same kinda thing, the girls who are too nice and perfect are too... easy? As in you almost take it for granted. Then you have the girls who play way too hard for even me to get and they end up not liking me as much. Exactly the same as above, just further up the pecking order so to speak.
You just gotta keep going until you find the one that clicks as cliché as that sounds.
All my relationships we really liked each other and never been like that. Yours almost sounds like puppy love or high school stuff. Just saying lol. Kinda like once you find the guy that really likes you you don't like him back as much. Honestly don't think your dating the right guys 😕