Pregnancy after stillbirth.

Ashley • Blessed with 2 boys. One angel baby Ryker and one 2 year old Troy. Trying for a Scarlett.
I lost my son Ryker on December 13,2013 due to my placenta clotting. He was a still born at 22 weeks. After I had him, I bled for 3 weeks, then 3 weeks later I had a period. That was Jan 21. We are trying again, not to replace our son, but to fill that gap. Anyway, since I don't know how long my cycles are, when would be a good time to test? I'm on cycle day 30.