Worried and need advice please!!!

So my periods have never been a consistent cycle I have gone months and months with no period and then get it. Well my last period was July 26th but I have had symptoms every month like I was going to get it. Anyways me and my husband had sex about a week or 2 ago and I started bleeding but it was very light and was gone the next day well for the past week I have had like a brown stringy discharge (no odor) and its very light only when I wipe and also some very dull cramping. I took a pregnancy test 3 days ago and it was negative but I have been a little Nauseated on and off and I had the flu like a week ago so I'm not sure if I'm still getting over it or if I could be pregnant. Any advice???