Emotions going crazy after birth

This is so strange that I am feeling like this but I miss being pregnant even though I was miserable during and was so ready to have my baby already. Maybe I am feeling this way because we are not planning on having more kids and this was our last one. My baby is 2 weeks old and I am so sad that I am not pregnant with him anymore. I am sad that time is flying by and feel like I can’t control my emotions. I am cherishing every moment with my babies but I cant help but feel depressed that I have a new baby now (not just my two year old,) and that time won’t slow down.