What Causes Cuts On The Side Of Penis After Having Sex?

My ex girlfriend and I got back together , after sex she gets small cuts on the sides of her vagina and sometimes I get tiny cuts on the side of my penis. I have not been with anyone else since our separation but she has had a few other partners. I m afraid that she has given me a std. I previously didn t have any stds and she didn t either. My question is what type of stds are there with those symptoms?