What Causes Brown Spotting With No Pregnancy Symptoms?

MY girlfriend and I had sex when the condom broke, I pulled out and did not cum. I pulled out as soon as it broke. this was in the end of may. She had brown spotting and some blood spotting for 4-5 days on june 6th on wards.. I do not think that she is pregnant. This happened over a month ago and she is not having any sickness, boobs do not hurt. She has been very stressed over this time frame though. Help please!