Menstrual problem. Is it stress induced?

I had intercourse on day5( 2nd April) of menstrual cycle. But penetration was incomplete...almost nil. He withdrew quickly before actual penetration could happen because ejaculation was about to occur. He ejaculated outside. I was sure nothing happened, but he wasn't so prophylactically I took a levonorgestrel tablet after 12 hours. I have a 28 day menstrual cycle ( sometimes 30). After that I bled on 7th April in the morning a little and a little bit in the afternoon. So is it normal? Is it because of the drug? I hope there's no chance of conception. If it's not conception, what could the reason be for the bleeding? Is it stress induced? Because last 3 days have been  very exhausting mentally.  Please reply soon. It's very urgent.