What’s the earliest you’ve tested?

I ovulated Sunday, or at least that’s when my positive test was. Can I test the beginning of next week? I’m very impatient. I also have been on BC though so I haven’t gotten my period yet. Fingers crossed and it won’t come!

Also - I know you ovulate like 12-36 hours after ovulation… but how would I know the exact day of ovulation & how many DPO I am?