Catching Grandma

I'm Andrew 18 and single, recently my father left my mother Joyce 36 and they are now divorcing. Joyce is a nurse and works shifts, I'm her only child and we moved with Grandma Fiona 55 widow as our house is being sold. Also Fiona's house is closer to the hospital Joyce works at and close to the college I attend. So I'm home with Fiona a lot the power in his neighborhood went out, a call to the power company told us it would be off for at least 2 hours. So I decided to return home, arriving home I came in the back door and got a drink from the frig. I then went into the lounge room and found it empty, so I went looking for Fiona. While walking down the corridor I heard a moaning sound coming from her room. I opened the door slightly and looked in, on the bed was Fiona rubbing herself with a dildo and fingering herself. Trying to get a better look I moved the door a bit more and made a loud squeaking sound and Fiona caught me spying on her. She was shocked at being caught masturbating and angry that I had spied on her. Then seeing I also had a bulge in my pants. She told me to drop my pants as I had seen her naked, it was only fair that she saw me naked. I dropped my pants and my hard cock poked out at her. She than told me I had a nice big cock and asked Have I used it on any girls yet. No, not yet I replied, then told to lay on her bed and she would get it down for me. She went and got a wet wash cloth and while still naked started rubbing my cock with it. It felt nice and I reached up and touched one of her breasts. She looked at me and I removed my hand, she told I could feel her breasts and touch her body if I wanted to. So I started to play with her breasts, I still hadn't come. So she threw the wash cloth on the floor and said I'll suck you off and you can lick my pussy. Getting over the top of me she put her pussy towards my head and with her head over my cock, she went down on me. I really liked her sucking my cock, but then stopped and said I had to kick her as well or she would stop. So I started to lick and I didn't tell when I was about to cum. I filled her mouth and she swallowed it all. It took a little longer for me to get her off as well. Than as we laid together on the bed, I asked her Could I fuck you, looking at me. She said We shouldn't, but after what we've already done. I think it would be alright to finish it with a fuck. But I'll be on top, so we had sex and then went to sleep. I woke up around 4am to go to the toilet and she followed me. After she told me to go to my own bed as Joyce would be home shortly after finishing the night shift. The next morning I went into the kitchen and Fiona was making breakfast. Joyce was sleeping in her room, so I grabbed Fiona and gave her a hug and a kiss on her neck. As it was Saturday no college and I asked Fiona for another fuck. She said Okay but not here, you never know when Joyce will wake up. We had breakfast and done the dishes and Fiona said If you still want to fuck me, we'll use the garage there is an old lounge in there. I head off to the garage and once I was inside Fiona followed. Since I've been getting sex every chance we get. When is at work or sleeping, Fiona is a great teacher.