Verify, you period was 14th March or April? It was 2 days long?
I'm thinking you meant May.
A missed or late period is a COMMON side effect of an emergency contraceptive. Your periods can be early or late, heavier or lighter than normal, you may have some spotting, you can have sore breast, all that. Symptoms can last for several months.
It's unlikely you are pregnant. You took the pill in time.
Good luck, hope it helps.