Unfortunately I am not which i suppose I really should and yes i wash my hands twice after masturbation its one of my many compulsions which i have to put up with, the things in your sentence above i have told myself as i do Biology A level so i know that I would be the first in history to ever pull off such a thing but my OCD just won't let me forget about it so it is constantly there and i constantly think what if, there was no visual sign i had any semen on my hand and i couldn't feel any thats why i answered the phone but now i am still anxious, Wow i really need to get my head checked out!
You are overreacting like crazy. Relax.
Even if you somehow managed to transfer sperm from your hand (After you cleaned yourself with a tissue) to a phone to your sister which, in and of itself, would be a fantastical series of events that would have to happen for you to get her pregnant... she's on the pill. So she's not going to get pregnant. Relax. Not pregnant.
You'd be the first man in history to impregnante a woman this way.
Are you having your OCD treated? Seems to me like you'd be more caerful about washing your hands after masturbating just out of basic hygeine.