Stretching the skin instead, am I doing it wrongly

Hi guys, I’m uncut and I’ve recently started PE. Today is my third day and after my stretching, I can see red marks on my penis skin.

So I would like to ask am I doing it correctly? I’m afraid that I’m just pulling the skin. I can pull the foreskin back, but when stretching, the frenulum(don’t know if I spelled it correctly lol) will always be painful, and still I feel the whole skin being stretched instead. I can’t just grab the ‘head’ as it’ll slip and more painful.haiz.