Long drive but horny

So the other day I was driving home and I was real horny. My sister was sleeping in the passenger seat wearing a skirt. She is about 5'11" weighs 350 pounds and has 36 DDs. She is not very attractive but I have always enjoyed the thought of fucking my sister because of the taboo of it all. So anyway I was driving and decided to start jacking off. I needed lubricant so i reached over and started rubbing her pussy. She is a heavy sleeper and did not wake up. I was rubbing until i felt her get wet. I then reached into her pants and slicked up my hand, and then rubbed it all over my rock hard cock and masturbated until i came all over my hand. I then dropped a couple drops of cum into her mouth and then started fingering her with my cum on my fingers, hope she doesn't get pregnant :)