I find that I become less attracted to girls once I find out

realise that you should only pursue girls who are already interested in you. if a girl is not interested in you, there is no point, and she will become disgusted by your continued pursuit.

if you're not enthused by a girl being interested, maybe you aren't actually looking for a partner right now and just prefer to be validated by girls that weren't formerly interested?

I'm not an expert but for me the grass is always greener on the other side, people always want what they can't have so if you have something you want something else
Its like buying a new corvette and a month later you sell it for a camaro
Or like when you get a promotion at work but you miss your old position more
Or when you were in highschool and all you wanted was to leave and be a free adult but now all you want is to live that simple life again

Op you actually have terrible self esteem and insecurity. You hate yourself so the second someone likes you, you wonder why they like you and then you think they could do better than you, and you lose interest in them. Get therapy or something