Bleeding after period ends

LizMarie • Loves anime, singing dancing writing, 20 years old, speaks spanish and English
I had sex with my hiusband the day after my period and i started bleeding when we finished,like a brownish red color, the next day we didnt have sex but i still blead. I freaked out and went to the hospital and they told me everything was fine. The next day i stopped bleeding. It hasnt happened anymore. I wonder why it did? Anyone know?