When you roll back your foreskin, it should sit underneath the head of your penis. When you have sex, it shouldn’t be painful, if sex is painful, then you should use some lubricant. If you don’t have a lubricant handy, saliva and the natural lubricant produced by the woman’s vagina should be enough to not cause any pain.
Note
It is important to maintain adequate penile hygiene while doing stretches or masturbation since the crème and semen tend to leave residue and that can be a cause for fungal infection. Try cleaning it with an anti-fungal wash such as Men’s intimate wash.