I would suggest try different brands of floss. Some are shit, some too slippery etc etc. Also practice and improve your technique. Personally I found the Colgate floss to be too thick and Oral B is best suited for me.
Also fun fact : the gap between all your teeth may not be same. Some maybe a bit more bunched up, be careful on how much force you apply. Too much force and it'll go straight to your gums and you'll end up bleeding.
Last option if you are lazy is use a Waterpik or some other dental water flosser.