Obsessed With My Roommate

I'm a 30 year old male and share a house with a 20 year old female. Neither of us own it, we just rent rooms. I find her very attractive, she has long black hair and a great body too. I've never seen her naked but when she comes back from the gym her clothes are so tight you can see every contour and her VPL, she often wears skimpy knickersthongs etc, I'm quite familiar with her underwear but more on that later. Once or twice she has been in the kitchen with a tshirt and no bra. The shirt was too thick to see nipples through it, but I got a good idea of the general took of them. She's by no means flat, and not busty either, but the look real firm and perky which just a slight jiggle when she has no bra. She seems very confident in her body and doesn't seem to mind walking around in tight or revealing clothing. There's one set of black leggings she has that when she bends over they go almost totally see-through, revealing her knickers in amazing detail, again usually a black thong. I'll be eating at the kitchen table and she'll be going about doing things, bend over and my cock just goes instantly hard, she might as well not be wearing any leggings at all. I wonder if she just doesn't know, or knows but doesn't care, or knows and is just teasing me.

She has a boyfriend and sometimes I hear them having sex. She is often quite muted and hear just basic grunts and groans, but on the rare occasion, when I think she thinks I'm not there, I hear her being slightly more enthusiastic. It always makes me super horny and I like to jerk off while it's happening. Even rarer is when I hear sex noises when I know she is alone, and that's normally around 2am or so, so I assume she is masturbating. I don't hear any toys or vibrators so I'm not sure if she has or uses them, or just sticks to her fingers.

A particularly shameful confession I have is that our doors lock, but one day when it was really hot she left her door propped open, I assume for a breeze, and when she was out I went into her room and looked in her bedside drawer as I thought that if she had a sex toy that is where she would keep it. There were condoms there but no sex toys. There was a brush on the table with a thick, round handle though and I wonder if she uses that to improvise with, if that handle had been inside her pussy. I gave it a smell but nothing unusual stood out.

My most shameful confession, though, is that if she's left her dirty washing in a basket by the machine waiting to wash it I'll examine the contents closely to build up an idea of her entire underwear collection. If I know she has gone out and I have time alone with the underwear I'll take some out of the basket, smell the crotch of her panties, especially the ones with more obvious streaks in the crotch. They always smell strongly of her pussy and smell amazing. Once or twice, again when I know she is out, I've taken a pair to my room to sniff while I masturbate, or maybe I'll wrap the soft cotton around my shaft. Most of her underwear is plain black g-strings, but she has other knickers too, some brighter coloured, or pink, red etc. Same with her bras, from what I've seen she isn't much of a lingerie type girl, unless she keeps that for special occasions.

She's a really nice, sweet, funny girl too and I enjoy the times when we get to talk, and I do sometimes feel guilty about what I do with her underwear especially, but she drives me crazy cos she is so sexy but unobtainable, I've lost count of the number of wanks I've had thinking about her.