Does this sound more like baby blues or postnatal depression?

I've had my second baby 9 weeks ago now. They are 18 months apart. With my first I felt this way straight away, with my newest baby I'm only starting to get like this.

I just want another baby so much it hurts. I don't know why, it's a natural feeling I can't get rid of. Maybe I don't feel complete with my children. I appreciate them so fucking much and love them to absolute bits. But WHY do I feel like this? Why does my body and mind never feel complete? I always wanted three children. But I'm young, 26 and still have time. I can't get rid of this and I'm not entirely sure what baby blues is but it's starting to piss me off. Anyone experienced the same?

I'm definitely waiting at least a year from now before ttc.