Implantation spotting.

Can anyone tell me if they have experience my situation. I got my period last month on 7/24. I'm on birth control using the patch. Me and my partner have had unprotected sex all during the month and he has finish inside. Now on august around the 16 I stared to feel sick. I couldn't eat anything I was feeling nauseous. I got what I thought it was my period two days earlier. I never have a really heavy period but is not light either is in between. I notice I was spotting I was wearing a penny liner and there was just very little light blood on it. I when to the doctor today and got a pregnancy test done. It came back negative. My doctor told me it was my period because the days were so close from each other. I know my body and I'm sure is not. I have read so much stuff on the internet and I feel like I'm having implantation spotting. The spotting only lasted for 2 days. I'm so confused my test came back negative is there any way I could still be pregnant ? Should I get another test done after a week or so to see if it comes back negative or positive?