What Causes Bleeding In The Mid Of The Menstruation Cycle?

HI, I took emergerncy contraceptive pill on 23rd April as I doubted there was condom failure.My regular period date would have been 9th May but On 30th April I started bleeding which lasted for about 3 days and was in every sense like my normal period. Today I am bleeding again but not much (Also the blood is red in colour just like my normal periods). should I bother taking a pregnency test?