Grandma tied me up

I had spent many evenings staying at my grandmas house when my dad went travelling for work. I would watch a lot of porn on the computer which was situated in the living room and my grandma caught me masturbating more than once. The first time she walked in on me I was jacking off into a pair of her socks and she made me cum on the floor so I had to clean it up. I already had to gun really bad when she walked in and even though she seemed mad at me she tickled me and tickled my cock until I busted everywhere. The second time I was caught, I was ass naked in the chair and she made me show her what I was watching. I was so turned on that I stood up and started openly jacking off towards her. She was wearing a nightgown type of dress and as she started to walk away I grabbed the nightgown and lifted it so I coukd see her ass. She batted my hand down but I was already on my knees and started sniffing her ass really loudly as I was stroking. She grabbed a pair of pantyhose and quickly tied my hands together and made sure I couldn't get out. She sat on the bed and watched my cock twitch up and down with a full boner. She squeezed lotion on my bare ass and spanked it hard until it was red and it hurt really bad. She took a pair of used panties and stuffed them in my mouth, tying it shut with a stocking. I could tase a strong combination of sweat, ass and pussy. Then came the flicking game where she flicked my cock back and forth, my precum oozing out. Making sure I could see, she stood in front of me as I sat on the bed and very slowly lifted her nightgown up so I could see her fat wrinkly ass. She didn't have panties on and I had to cum so bad I tried to get up but she laid me down and sat on my face. She out her whole weight on my head so my nose was basically in her asshole. She bent down and spit on my cock, flicking it some more before tickling my balls and right before I exploded a massive amount of cum she got off my face and stopped touching me. It was absolute torture and my veins in my cock were bulging out. After a while she came back and spanked me some more, the whole time my cock was slapping my legs. I couldnt speak but I wanted to beg her to let me cum. At one point I got up to run down the hall and she chased me. I got to a closet and hud in there but she found me and sat back on my face, this time facing me so I had to smell her old hairy vagina. It was wet and she had been touching herself off and on. Teasing my cock some more she dangled a long sock over the tip, barely touching it. When she saw my orgasm coming she aimed my cock at my face and I came all over my face. She left me tied up with my cum hardening but eventually let me go. I ended up touching myself right when she untied me and I chased her into her room where I forcibly took off her nightgown. Without putting up much of a fight, I slid my cock in her pussy from behind and fucked her really hard. I ended up cumming deep in it and I never had better sex in my life with anyone. Since then she sometimes lets me fuck her but I usually don't last longer than a minute. My grandma is a little older now but every now and then she gives me blowjobs