When should I buy a pregnancy test?

Anonymous
My period is scheduled one week from today... I had unprotected sex a week ago Saturday and Sunday on my highest ovulation days. Earlier today I felt a throb in my uterus and just now I was wiping and I noticed light, but pink blood. Should I wait another week or should I buy it now? I might be just a bit excited :)

ps. I've never had cramping or in between period bleeding, but there is always a first time for everything!
When should I buy a pregnancy test?
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