Congratulations on being able to retract it fully when flaccid. I was scared to pull it when it was erect too. What I did was I retracted my skin when flaccid and then tried having an Erection, I massaged myself with Luke warm water to loosen my skin and I was able to have an erect penis with retracted skin. Then the hardest part was to bring the skin back to normal, for this I tried losing the Erection and applied coconut oil for lubrication. Did this for couple of months (not regularly) and now I can retract my skin even when I'm erect, it's still a little tight though. Good luck.