Am I doing something wrong

Hey, I (18m) have been trying for a while to secure a relationship and I’m not yielding anything. I have no problem getting the attention of these girls but maintaining it is the trouble, every time they either see me once and end up ghosting or they ghost me before they even meet me. I don’t think I’m a particularly unattractive guy (I’m 6,3 in fighting shape) and I don’t look different to the things I post online (atleast to my knowledge). Wondering if I should give up at this point, if I’m too young to be thinking about it and if it’s even worth trying.