Depo injection (sensitive to some people)

So my last depo injection was on the 12th march this year, i felt all things pregnancy so i took a test last week and it was positive, fast forward to tuesday i ended up in hospital after having some spotting and the test from doctors not showing the line clearly, my tests are completely negative now, it turns out ive had a chemical pregnancy. When my partner and i found out i was pregnant again we were happy it would of been our 3rd baby and made the family complete, so weve spoke and im not going back on any birth control and were going to try again, but my main concern is how long it could take to get pregnant again, how long did it take you ladies to fall pregnant after having depo? Itll only have just gone over the 3 month/12 week mark now.