What Causes Bleeding After Intercourse?

hi,my age 27, I was lit bit bleeding after sex 2days before my period, I had a smear test done this Feb, result shows everything is ok, I don't know what's the problem. I had my period 27th march, but I had sex 25th and had lit bit bleeding ,and I should have my period 23re of APIRL,but I had sex with my boyfriend today, it was bleeding again, I 'm so worry bout now