Could I be pregnant?

Deanna
I had my paraguard IUD removed on Aug 16th (was on my period when I had it removed... Started my period on the 13th). I've had the paraguard in for 5 years. 
My boyfriend and I had sex without protection the week after. 
For the last 3 days (it's stopped now), I noticed light pink/brownish spotting, no cramping, just spotting. Thought maybe it could be implantation bleeding?? 
I've also been very very moody and tired and have been strong headaches. 
I'm supposed to start my period on the 9th, so I went ahead and took a hpt this morning and it was negative, so I plan on taking another one Friday the 9th. But could I be pregnant???