I agree that only you know if you are ready for another baby. I don't think there's any such thing as 'too soon'. I think your natural Mama's instinct can tell you whether you're ready or not.
That said, I agree that the healthiest way to go about closely spaced pregnancies is to wait to start actively trying until your youngest is 6 months old, so your body does have time to recover and is ready for another pregnancy.