Staring at Mom

I'm 28 now but this happened when I was just 15. It was a hot summers day and I was at home with nothing to do for the afternoon. I was lying outside in the sun reading a book when I decided to let the sun give me more of an all over tan and I pulled down my shorts to above my crotch. I didn't notice my mother come outside and she was looking at me do this in a funny way. 'You are growing up well' was all she said as she ran her eyes over my almost naked body. She was wearing a bikini and went to the other side of the house to lie in the sun. I watched walk away and wondered if she was going sunbathe topless. I couldn't resist having a peek and I waited before going around to see. Sure enough she had taken off her top and had pulled her bikini bottoms right down to barely cover herself up. I felt myself getting horny and I let my shorts slip off as I stood there. I don't know if my mother had seen me or not but she stood up, took everything off and began to rub oil over herself. When turned around and rubbed the oil over her ass I nearly came - I hadn't seen anything like this before. My mother was not yet 40 and kept in good shape. I must have made some noise because my mother looked around and saw me standing there naked totally erect, harder than ever. She said nothing but I think she liked what had happened because she didn't stop, acting like I wasn't there she continued and lay out again. I went straight inside, lay on my bed with a magazine and let rip, gasping and groaning, so turned on forgetting that I was making a lot of noise. Suddenly I felt a hand on my back - my mother. I stopped and turned around still helpless with horniness my dick like a rock in front of my mother. She picked my magazine and asked me which girls I liked more and why. She was wearing her bikini again and I just lay there as she showed me each picture. 'Go on' she said, 'I know what you were doing. I want to see, I know you were watching me'. I began to jerk really hard with my mother watching. She turned around and began to strip off. I reached out to touch her ass and she slapped my face real hard. Her breasts were in my face when she did that and she pushed me back on the bed telling me to never do that again. I didn't stop jerking I didn't care. She was shocked I didn't care and just stood watching while I ran my eyes all over her body. She must have realised I was about to come because she leaned down against me and I grabbed her, I could hardly breathe. She let out a weird noise and was breathing real heavy. I put my hands everywhere, mad with horniness. I opened my eyes and exploded with cum my mother was shouting and making sure I came all over her thighs. I lay back and she felt me everywhere until I got horny again and she jerked me off, a real weird look on her face. She asked me to cum on her ass, she turned around and I rubbed my dick against her before cumming again. She was going at herself crazy now and she must have cum too because fell onto the floor when I had come and lay there for ten minutes. Since that she didn't say anything about it but I know she watched me in the shower and always burst into my room when I was naked. It didn't bother me at all, I used to go into her room at night when my father was away and pull down the bedcover and look at her sleeping in her underwear while I jerked off. I know she used to wake up. I found out I was adopted later on and that it all weirder even!