Help plz? Teen health?

Hi im 14 and im still a virgin, i recently found out about my tight foreskin and so i have been doing stretching to losen it which has been working, now i can basically pull it all the way back but sometimes the foreskin slips and covers the head again - like it cant stay in place for long, so my question is that when your having sx, does your foreskin stay back constantly or does it move and go back and forth as you thrust? Thanks