How early can you take a test??

I need help.. I had intercourse 12 days ago & during that week I missed a pill. Im on the mini pill so I don’t get breaks, therefor I don’t know when my period is due, I started spotting 2 days ago & it’s been on & off until today. This morning I had bad cramping in my lower back & stomach. I’ve had headaches, slight nausea. Because I don’t know when my period is due I don’t know when to take a test, I’ve taken a test every day for the past few days & they’ve been negative, is it too early or are they just negative? I feel like it hasn’t been that long x