So i feel this alot. I like to second doubt or guess myself. I'll be pushing and pulling with a girl and flirting but than i shit myself. "Is she doing this cause she's being nice? or she likes me" i see ioi's that i don't see with outher guys, but that's because i act differently? I realize just now as I write it out, there's obviously some attraction. But my question is, how do i determine being nice? or having a genuine intrest in me? It's definitely something that has caused me to second think and even lose confidence and attraction towards the girl.

THis isn't just on one girl, this is on a wide pool of girl just fyi since i saw above. This is a lot of Day Game by the way. So a lot of these sets tested on are day game results

In my opinion your thinking to hard into it in terms of "being nice"
Based on my experiences and as you probably know, day game moves at a slower pace than night game. I only bring my target to a seduction location if I'm positive I've escalated not just comfort but sexual attraction.
Try night game out and see if your getting the same results.

Hope for the best,
Arrow