It sounds like it could be an infection. Take a pregnancy test, just to be sure. You can take one when your next period is due.
Well it's unlikely you are pregnant because you wore a condom, and thought it broke, but it turns out it DIDN'T break, but you still pulled out the unbroken condom, and put on a new one just incase (good idea), so you were protected the whole time, but keep in mind condoms aren't 100% effective, and you should always use two forms of B/C. Also, judging by the info you gave, you ovulated right around the time you had sex, so it's possible to be pregnant. You can test now with a first response early response, (use first morning urine) and get a positive if you are, if it's negative, wait until your period is due and take another test, if it's still negative you should schedule an appt. with your OB/GYN and let them know what's going on because it could very well be an infection causing the brown discharge. Also, NEVER let anyone finger you with dirty hands, ESPECIALLY after working on cars all day and not washing their hands, that can lead to some MAJOR infections. Good luck!