what feeling is it when I feel frantic and what is it called when I get that pleasant throb?

Hi, I was confused about mastebating. Like, I use a pillow and after a while I get frantic and have an urge to go faster and then a feeling like a pleasant throb comes, so am i  coming or having an orgasm or what? And I've used my hands before, but now i dont get much pleasure from it. And I have to do it when my mom can't hear me. But mainly what I wanna know is what feeling is it when I feel frantic and what is it called when I get that pleasant throb? btw im a 14 yr old girl