My mother was left on the doorstep drunk by a taxi driver and I had my way with her

I often was up at night when my mother came back from a night out and never thought much about it .
My mother had me when she was 13 so she still young herself now I'm 18 she only 31 and fit ,single and likes the night life now I'm old enough to forget about .
So this night I was on my playstation and I heard a car door and then the door bell ringing so I went down stairs and as I opened ed the door a taxi drove away and my mother was slumped in the doorway and I must admit this was the first time I had looked at her in a sexual way as her blouse was revealing her bra and she had short denim skirt on and black tights .