I've been there, and still am. I started smelling my stepdaughters panties when she was 15 (she's now nearly 19) as well as reading her journal for sexual writing, and masturbating into her panties. The most difficult part of it is the dreams that come at night, with her coming on to me. I equally fear and desire for them to come true.
Last year while she was laying out in a skimpy bikini in the yard I watched her with binoculars from an upper window, the glasses allowing me to see her camel toe, her engorged and hairless pussy protruding against the thin material. I've never found a single hair in her panties in all these years, and from her journal would guess she's been shaving since 16. I also enjoy seeing her at night in just a t-shirt before bed, her large breasts and nipples pushing through the thin material. She's talked to her mom and I about watching porn, how she likes it, and using an anonymous email account I have sent her links to things I think she might like, masterbating later with the idea that she is enjoying them. I hope someday she will respond to the emails, and may even send me pics of her.