Had bfp last friday and last saturday i had a chemical pregnancy. how do i know when i'm ovulating?

the doctor said it's ok for me to start trying again since i was only 4 weeks pregnant when i had a miscarriage. i used ovulation test when i got pregnant last month, but how do i know when to start testing again? was day 1 of my cycle when i started to bleed with early miscarriage? or will i get another "actual period"? i hear so much from people saying they got pregnant immediately after a chemical pregnancy, so i'm keeping my hopes up.