Helpful Nan

It started when i was 15 my nan left a disc out for me and said i should watch it when she leaves,I did soon as she left and was completely shocked that she gave me porn,she was interested in finding out if i had wanked off,when i told her i did she had a big smile on her face,over the next couple of weeks she would ask for details about my wank session,i was still 15 at the time when i was it was the day i would go round when she would be going out i messaged her if i could come round early and that she might give me a helping hand,I was just trying my luck,she didn't say yes or no and when i turned up she was dressed very slutty,she told me to drop my shorts and sit back and relax,for her age she was still hot,I sat there for 10-15 minutes with a boner leaking so much precum and wasn't aloud to touch myself, finally she said to me i think you're ready now she sat down next to me took hold of my cock and pulled my foreskin so far back i thought she was going to do some damage and she kept on the head was purple,I was glad to cum,when i was cumming she called me a dirty fucker look at the mess you're making,my worn out dick resting on my leg i asked why she done it like that and she said well it stopped you from ejaculating fast didn't it,it hurt but i kept going back for more that was a great time for me.