Pregnant Mandy Moore is battling a skin condition she says is the “pits” as she awaits the arrival of her third child. The 40-year-old ‘This is Us’ actress – who has sons August, three, and 19-month-old Oscar with her 38-year-old actor husband Taylor Goldsmith – has told fans she has melasma, after announcing in May she is going to be a mother again. She said in an Instagram post that showed her with a skin device: “Pregnancy melasma is the pits.” The gadget she was using in the photo was a Lyma Laser, billed as giving “unrivalled results” on “signs of aging, wrinkles, rosacea, pigmentation, s…