Help!

Ladies I need your help! So it's been 4 days since I missed my period, but on the day I was supposed to start I had a very light brown discharge but it was so light I couldn't wear a tampon. That only lasted 2 days. I took a pregnancy yesterday morning and it came out negative and again today and it came out the same way. My fiance was visiting for the weekend of August 27 (which was the day after my ovulation). On the day before I forgot to take my birth control and didn't realize it until the 27th at night when I was about to take it. I don't know what to do because I haven't had a legit period and the tests are coming out negative. PLEASE HELP ME!