Pregnant on depo?

I got the depo shot for the 1st time on April 29th...havent been on any BC in over 2yrs....Hubby and I had unprotected sex on may 1st and everyday since then. I ovulated on the 3rd. Ive had sore nips and cramps all week.

So my questions are is it possible for me to be pregnant?

Ive been franticly googling and see mixed notes on the effective time period of depo some say works 24hr, 72hrs, 7days. Which is correct?

If i did get prego before it was effective will it cause a miscarriage now that it is effective?

Sorry for the longwinded question but im super worried, we're broke and baby #4 is not a option