period vs implantation bleeding

Hi, I had sex and I was spotting,which was only noticed after having sex.  I thought I was starting my period early, so I took out my nuvaring.  Since then, it has basically been very light.  I've always had heavier periods.  I thought about it more, and I never start my period until 2 days after I take out my nuvaring, which is like clockwork for the past few years.  I usually use 4-5 super tampons during my first two days of my period and now I use a junior one everyday for the past 4 days, and it is very light.  Do you think that I could be pregnant?  

[1pretty]

also when is the earliest that I can take a pregnancy test?  I usually take out my nuvaring on the 10th and have a heavy period on the 12th