What Causes Pigmentation On The Head Of Penis With Lack Of Libido?

For awhile now it seems I haven t been able to get excited as easily any more, and when masturbating, which I haven t done in a few days recently, doesn t feel as good, I don t know if It s because I m just not horny and trying to masturbate anyways, but I ve noticed that the tip of my penis is more pale than the rest of my penis head, I have no clue is this is just my skin colour ( I am white ), the rest of the penis seems to be of normal colouring, I haven tmasturbated for a few days, but I could get an erection then and seem to be able to urinate fine. Can someone please tell me if this colouring is okay and if they have any idea why I seem to be wanting to masturbate less/not getting excited as easily etc recently? Thanks alot.