What Causes Vaginal Bleeding After Intercourse?

Hii am 25 yrs married woman. i got married on 5 dec 2009.my periods was due on 11 dec but i got on 1 jan,then i again missed the due date and got period on 21 feb.in between only one preg test was positive but all others were negative.then got prd on 20 march,and then on 27 april. when next date was due i got spot of blood and brown discharge twice or thrice and i got period on 7 may,i did sex with my husband on 17 and 20 may.when i went to washroom after 6hrs of recent sex i got lot of fresh blood when i urinated and then no blood throughout the 2 days and got slight fresh blood again when i use to urinate.......i am quite worried wats happening to me.i am having slight uncomfomfortable feeling on my lower abdomen and back and some time feeling of tiredness and i am eating less from the last 3 days., may I answer your health queries right now ? Please type your query here...