May have tested too early?

I tested at 5DPO and got a negative. (this is my first time not having to pull blood to see if I'm pregnant). I'm now 8DPO, Yesterday I've felt some painful twinges in my lower abdomen and have had really sore boobs. I have 5 days until I possibly get my period. any idea when I should test? before my due period or after it should be due?