How early do you test?

Tay • 36 years old with a 6 year old daughter and a 2.5 year old. Miscarriage in 1/15 and 6/15. I am expecting again in December 2018. ❤️😍
My period isn't due for four more days and I'm freaking out because two were negative. I'm so freaked out about my MC and TTC that I'm just setting myself up for disappointment. I realize it's early.