Like said above, no. Any medicine anywhere has the potential for side effects. As for preventing, that's done by using proper protection before the act ever occurs. Afterwards, there is nothing else to prevent other than EC and even those don't always work.
I really don't think there are any contraceptives without side effects other than abstinence and condoms. I've been on 3 different forms of birth control in my life and all have their own side effects, but unless you're really sensitive, none are that bad.