It could be, or it could be caused by various other things like infection, or maybe even the sex, although I've never personally had spotting after sex until I got pregnant. Are you trying to get pregnant? If so, I hope you get your BFP! :]
I went through the same thing as you, and I just found out I'm pregnant yesterday, so it is very possible you can be. Hope this helps.
Thanks Gerry and Kimberlee for your replies. We are ttc. I really hope its implantation bleeding. I'll keep you posted.