Fun with my mother-in-law

Im a 22 year old guy who just like most other guys is always eyeing up loads of women. Since the age of 16 I have had many sexual encounters with girls and for the last 20 of them I have started keeping a momento afterwards to remind me of the great fun we had. It all started as a mistake after a girl I brought back for a one nighter left her thong on my bedroom floor. I woke up to find it there and began to relive the past nights love making. I suddenly had this urge to be with her again when I spotted her thong. I began to slowly masturbate my hard cock whilst looking down at her knickers with a slight stain in them. The next thing I knew I had the crotch of her thong pressed directly to my nose, smelling her scent. It drove me wild, I wanted more so I started to lick the stain, still being able to taste her juices on the now increasingly wet material. And that is where my fetish for it all started.
Since then I have kept a pair of panties whether they were given or if I had to steal them and every now and then I go through my pile of dirty underwear having a sniff, reminiscing the night of pleasure provided by the wearer. Now I may begin the story…..
I had just finished work and didn’t want to go home to my cold shitty flat so I decided to go to my girlfriend Jenny’s house. She lived at home with her mum and dad still but they were relaxed with me going round and staying over. When I got there I knocked on the door and it was Tina who answered. Tina is jenny’s mum, she is roughly 45 years old, id say about 120 pounds and maybe 5ft 7 tall. The years have been good to her as she still has a fantastic arse on her, pretty small but perky looking tits, and a slight belly growing. Her hair is brown and shoulder length, and she flicks it round in a flirty fashion often enough knowing that people still find her really attractive.

‘hello john, what can I do for you ?’ said Tina
‘I’m just wondering if jenny is back form work yet?’ I said
‘No, but she shouldn’t be too long, come in and wait if you like ?’
So in I walked watching her as she looked to almost glide across the kitchen floor.
‘fancy a brew?’ she asked
‘yes please’
I watched her in my usual admiring way as she worked her way round the kitchen opening up the fridge to get the milk, looking in the cupboard for the tea bags. She was wearing a white blouse with a frilly pattern down the front where the buttons are, a black knee length pencil skirt, black tights and heels. This outfit really made her look gorgeous, like a really sexy little secretary.
‘ Paul not back yet?’ I asked with a glimmer of hope
‘no, he is working down south this week so wont be back till the weekend’
My heart started beating, Paul was her husband, and with him out of the way it made it a whole lot easier to complete my fetish.
‘is it ok if I go use the bathroom please ? I asked
‘yeah sure, u no where it is’ came her reply
I had the usual excited spring in my step as I started to so up the stairs, two at a time. I knew I didn’t have long so every second counts. I walked along the corridor towards the bathroom and opened the door then shut it again pretty hard without actually going in, hoping she would think I was in there.