I am studying my +2 now, facing problem everyday and struggling to control it.
My parents are teachers and we are living in small home. My mom and me used to sleep in king size bed ( since my childhood) and dad used to sleep in seperate bed otherside as we have one bed room only. We used to have mosquito nets around our beds.

When I was in high school, once I noticed mom was going to dad's bed and they used to have sex. Typically they used to do it in middle of night after I asleep. I have been used to see it half open eyes in that bed light whats happeing inside their mosquito net.

Once after they had sex, mom came back and slept beside me as usual.
After she went to sleep, i went close to her and hug her butt from back and slept. She was in asleep and did not much noticed me even she moves from this side to other side.
This has developed more attached to her and now some times I go close to her and hug her and sleep. It was fine upto here but I was not able to control my feelings, started trying to do more.

Once my dad went to banglore, I noticed her saree was up and noticed that she had no panties, I tried to do something it did not work. I did not do any sex. She never got angry on me when I hug her from back and sleep.

This is caused bad thoughts in me to do sex with her, I know its wrong and she will not accept it. How do I control these feelings from me and be nice boy and focus on my studies.