I had the depo-provera shot a week after the start of my last period. what would be the chances to get pregnant if had unprotected sex and he ejaculated in me?

Uncertain risk: Assuming that you had unprotected intercourse after your period, and after the start of the Depo-Provera shot, then your chances are probably lower than the baseline risk of 15-20%. Given that you imply that you had intercourse not long after starting the Depo-Provera shot, then the risk is higher than it will be in about a month. Without more information, it is hard to give you a better answer. Check a test!