How to calculate due date after miscarriage???

Caitlin

I started miscarrying on 6/1. I passed all the remaining tissue on 6/12 but still had some light bleeding for a couple days. I tested positive for pregnancy again on 7/3 with a vvvfl(but we monitored my levels down to 0 so I know it’s not leftover hcg). Problem is I don’t know how I calculate due date now. Does anyone have experience with this?