Where's my period?

Hayley
This will be a bit long so I apologize in advance. So my last period was June 3- June 9. It has been irregular since I started my period, which was about 6 years ago. I had sex for the first time on June 13, yes we used a condom and no it didn't break. I had scheduled an OBGYN appointment in April because I had my period for 2 months straight. My appointment was on June 22, and I went. He prescribed me birth control and told me to take it on the first Sunday of my period. So I've been waiting for it. Well since it still hasn't come, to just ease my mind I took a pregnancy test on July 23 and it was negative. I talked to my primary care doctor earlier today and he referred me over and is having me get an ultrasound done to check everything out. Now it's later in the day and I am having very little brown spotting and I was just wondering if anyone else has experienced this before. Or if anyone has any advice for me?