Remedies for hyperpigmentation?

i started getting dark patches on my stomach, behind my neck, on my lower back, upper pecks and sort of my arm pit area and from what ive googled I THINK its hyperpigmentation. If its not someone please correct me, but if it is do you guys know of any remedies for this? to make it go away fairly quick, i have to go on vacation soon and this has been rather ruining my summer since i obviously dont want to look like the weird kid with discolored skin on the beach, and also the next dermatologist appointment is in NOVEMBER, i will not wait that long, so if you guys can even help lighten it a little or even better make it go away i will be extremely generous