Plan B One-Step - Does Plan B work for more extreme incidents?

So my boyfriend and i had unprotected sex, ( I know, BIG no no) but I am really nervous of being pregnant. I finished bleeding from my period two days before. We had sex 2-2-15 at 2am and I took the pill at about 1pm that same day. That same morning (about 8 hours after) i was feeling nauseous and had a decent headache. Its currently 11:30am on 2-3-15 and im still feeling light headed and my stomach is upset. Should I be worried and look for more options or should I just wait it out?