Forgotten Birthday

Last month I forgot my mother's birthday, Grace 45 divorced and me Lionel 22 only child live together in a 2 bed apartment. We're both average in looks and build and not really into the dating scene. We go to our jobs and come home and rarely go out at night, my father Donald fucked off 5 years ago and hasn't bothered to stay in contact with me. So Grace and me keep each other company, anyway last month I was busy trying to get a higher paid job at the company I work for and forgot about Grace's birthday till on the way home on the evening of her birthday. I quickly stopped and tried to find a gift for her, but there wasn't anything I thought she would like. So I got a nice birthday card and wrote Slave for a day of your choice and will do anything you want. Grace liked having her feet tickled and massaged. So I thought that what she would most likely want, I don't like doing that all that much. But it would be something she would enjoy. At dinner that night I gave her the card and waited for response. She said thankyou and I will think of something and that was all. Being a Wednesday I thought she would wait till the weekend when we would both be off work. The Saturday Morning I was up early and made breakfast for us both, during breakfast Grace said she would take me up on my offer of slave for a day birthday gift. As I thought she wanted me to massage and tickle her feet. Then she surprised by saying I had bath her and massage her back after the bath. But a promise is a promise. After her bath and drying her I started to massage her back, both still naked and while massaging her I got a hard-on. See saw it when she turned her head and just smiled at me. After massage she told me to fuck her and not waste my nice hard cock. I thought might as well and mounted her and leaving my sperm inside her, while lying beside after the fuck. She thanked me for the best birthday present ever, I told her the day isn't over yet. I know she replied and she started to play with my cock. Then she started to suck it and I started to lick her pussy. We ended up fucking again and we continued to play around with each other for the rest of the day and the Sunday morning as well. We went out and got lunch around 1 pm and on getting back home I gave her a feel up and she said the birthday day was finished. I replied how about a fuck for a fuck sake. Alright let's fuck she answered and we have been fucking and sleeping together ever since.