Am I Wrong For Listening?

I am a 20 year old guy who moved back home between my second and third year of university. My mother is 45 and when I left home for school she sold the big house where we had lived and moved to a two bedroom apartment. I went to summer school after my freshman year so this is the first time that I have been living with her for almost two years.

Her new place is tiny and the walls are paper thin and during my first evening at home I woke up to sounds in the next room where her bed is very close to the common wall. At first I didn't believe what I was hearing but then as I strained to hear there was an unmistakable humming sound. I wondered if it could have been the television set until I began to hear her heavy breathing and gasps. The sounds of her masturbating continued for a long time, longer than I usually take when I am jacking off. Then there was the unmistakable groaning and gasping of her orgasm followed by silence.

When she finished I was so sexually turned on that I just had to jack off which I did while trying to be discreet and quiet. But thinking that she was asleep I let myself go when my orgasm came. I was just about to go back to sleep when her sounds began again and as I listened I became hard as a rock for the second time. This time I jacked off as I listened to her and had my own orgasm at the same time that I heard her gasping with pleasure for the second time.

It seems obvious that she must have known what I was doing but we have not mentioned it to each other. And since the first time it has happened several more times. I'm not sure what to do or if my eves dropping is wrong.