For almost a year now, I've had these lines on the glans of my penis. They have the same

appearance as dry cracked skin, and are more visible when I have an errection. The lines are also imprinted on the inside of my foreskin (the part which covers the glans).

I saw my GP about it, and she said it was normal. I don't think so.
I've tried applying E45, moisturiser, etc. none of which had an effect. Google was pretty hopeless, I haven't seen any pictures or information on this condition.

Have any idea what's wrong?