What Causes Cervix Bruising?

i have been with a new partner 4 times now the 1st time and this last time i bled adn it has freaked him out. I had my period 2 weeks ago and after the 1st time i went to my dr. they told me i had no STD's and she said my cervix had been bruised. This has happened with other partners I have had. My question is how can i not have this happen? not only is it embaressing it is becoming really upsetting?