Implantation?

So I think I ovulated exactly a week ago and today I have been cramping a little. I just went to the bathroom and a little brownish spot was on my underwear and when I wiped it was a little pink and a some brown. My period is supposed to be here Wednesday so could I just be starting early or is it implantation? When can I take a pregnancy test? Any help would be great. He is so anxious and has been hounding me for the past 20 minutes about it! 😊