light spotting ?

I should have started my period on the 10th, well yesterday I thought I started when I got up for work and wipped and noticed blood. Well it's not normal to me. I have a pretty regular period and this is very light spotting. Like I've had the same pad on since 10am and it's now 4 and there's two little drops and that's it. I took a test yesterday and it said negative. I do have an IUD. Could I just be over thinking and freaking out? Should I take the other test in a couple days?