Nexplanon question

Cheryl
I had my nexplanon removed on August 11th and had what I thought as withdrawal bleed after that for 5 days...I started ovulation testing on August 16th....my ovulation peaked on August 27th...so I'm 12DPO...I took a test this morning and BFN. My question is do I need to have a period before I can get pregnant or did I test to early? Any advice would help!