Need advice about the Depo shot!

Hey guys , I’m 16 weeks post cesarean and For contraception i decided to go with the jab in the butt since I am breastfeeding and that was the best one for me. I have never been on it before and have only had one period and was due my second period 9 days ago haven’t had any spotting or anything.

I don’t want to be pregnant again as I had a emergency cesarean and was recommended not to be pregnant for 18months min.

Does anyone have any advice on the contraception jab please? Thank you so much xx