I Blackmailed my Grandma

I'm Dan 21 and a bit of a nerd, skinny and wear glasses and into sci fi and things like that. I also visit porn sites on the web. Three months ago I was looking at a Granny Porn site and saw my Father's widowed mother Grace 61. At first I wasn't sure,but then saw a tatoo of a blue betterfly on her shoulder and then I was sure. I downloaded the vid and waited till I could see Grace alone. The following Saturday I went over to Graces to mow her lawn. Dad usually does it but was out of town for a Classic Car Club outing. Mom was with him and I had agreed to mow the lawn. I took my laptop with me, Grace was good looking for her age, slender with nice set of tits. She was always well dressed and happy to see me. After mowing the lawn and while sitting on the patio with Grace having a cold drink. I opened my laptop and showed Grace how to operate the laptop, I had the vid marked Most Favorite on the desktop, I left to go to the toilet. But watched her from inside hoping she would open the vid file. She did and at first she didn't realise it was about her, but as I returned she did and went red in the face, she looked at me and said "How did you find this, it's 8 yrs old was taken down 5 yrs ago". I replied " Once you post anything on the internet, you cannot fully remove it. Someone somewhere might have downloaded it and reposted it later on". She said "What do you want to get rid of it". "I don't want money and won't show anyone else. But would you please teach me about how to please a woman sexually. I need to get some confidents where girls are concerned". "You want me to teach you about sex, you want to fuck your own Grandmother". she replied. I replied "How else am I going to get confidence to meet girls, I'm too shy even to pay a girl for sex". She was quiet for a while and then took my hand and led inside the house and to her bedroom and said "Not a word to anyone and you get rid of it off your laptop, Alright". I agreed and we spent nearly 4 hours with her teaching about having sex. Sunday morning I return and we had other lessons during the day. After a couple of months my confidences was a lot high than before and I still getting help from Grace.