sorry for your loss. My doctor made me wait one full cycle.
I am so sorry for your loss (((hug)))
As far as how soon you can try again, you should be on pelvic rest for 2 weeks (so no tampons or intercourse). The most doctors recommend waiting 2 or 3 cycles...not only to allow your body and cycle to return to normal but also so you have time to process your loss and go through the grieving process.
That said, there really isn't a hard and fast rule. Some people try again right away, others wait.
Best wishes to you