Sometimes my foreskin slides forward too… as long as you’re applying enough pressure to push the blood from the bottom of your erection to the top, you should be fine.
Please keep in mind… I’m not trying to say that you need to apply a lot of pressure, or, more pressure than you already are…
You don’t want to injure yourself…
I’m simply saying, that as long as you’re pushing the blood from the bottom to the top, you should be just fine… even if the foreskin pulls upwards a little bit.
Just make sure that you stop when you get to the head of the penis (it’s ok, if sometimes you accidentally go past the line where the head starts… just try not to do it everytime/all the time).
I might suggest jelqing with a 90-95% erection, since, you’re starting out with a 4inch erection at 100% and are having trouble with the extra foreskin…
This will help you to avoid pulling so much foreskin…because, the penis will be filling more of it up.
Just keep in mind, that if you do choose to jelq at 90-95% (or, even 100% erection), make sure that you aren’t applying a lot of pressure… you won’t be able to apply the same amount of pressure as you would when jelqing at 60-80%…
Also, it should be noted… that as long as you’re making slow and steady jelqs, with the right amount of pressure, the top of your penis will be extremely red (full of blood).
As compared to just masturbating, which usually doesn’t cause any redness whatsoever.
And it should never hurt, or, cause pain.