You need to see a Dermatologist as soon as it is possible …
Dear greg,
Have you noticed other symptoms, such as tightening of the foreskin (if you have one) or the pee hole narrowing? Your photo suggests you may have a skin condition called lichen sclerosis (aka balanitis xerotica obliterans) and as wee_dugie suggests you should seek advice from a dermatologist to confirm the diagnosis and start some treatment. If all you have are these white patches and nothing else wrong with sexual function or how you pee, then you probably just need supervised treatment with a strong steroid cream like Dermovate. If the foreskin or fraenum are getting progressively tighter and you can no longer pull the foreskin back (if you have one) or your pee hole (meatus) narrows you should consider seeing a urologist.
I’ve annotated your photo to illustrate these points.
Rgds,
Adhari