Short answer: you were late to respond or commit. In your mind you must be dropping obvious hints, but given today’s culture, it’s pointless unless it’s explicit. If it happens once or twice, it’s the other guy. But if it hairs frequently, it’s likely you.
Longer answer: You have omitted a lot of info into this post. One clear thing is you start by playing hard to get. In this age, no one will be talking just to you. They also assume you don’t do it either. If you are making the guy do the work, win your trust, affection, be interesting, charm you, convince you they are the one, they will expect an answer quickly. If you are late, it’s mostly taken as no. They have options, talking to multiple girls, and you were just slower than others. Or unsure. A guy can only charm you for so long till he infers that you are not interested.
One thing you could do is lay out how you think instead of the guessing game. I remember this one girl telling me she wants to wait 2 months before committing, i appreciated it. Moved on from her, but it was great that she was honest and i didn’t have to figure that out.