I doubt your pregnant, esp. Since your daughter is only 4 months old and you got the shot. Your body just isn't prepared yet for another pregnancy. Don't worry!

They are both just as effective (the pill and the shot). As for the 4 months part.. Her body is just as ready as it would be normally.. In fact you are more fertile than normal the first year after pregnancy (i have some friends who found that out the hard way). However, in your case the shot is very good at protecting you. It never hurts to get a test if you are really concerned.