Brown Spotting After Unprotected Sex, Bloating, Headache, Swollen Breasts

I had unprotected sex after my period in august. four days later I was able to get plan B. Ten days after that I began spotting brown on and off for two weeks and then one day of red. I took a pregnancy test that was negative, but have been feeling bloated, having headaches , swollen/heavy breasts consistently for the last week so i took another test and that too was negative what are your suggestions, could it have been a false negative pregnancy test. I have never in my life felt this way before