Is it just baby blues?

My son will be a week old tomorrow, and I keep crying once I think about how fast time is going by. I was miserable at the end of my pregnancy and just wanted him here; and now that he's here I get so sad bc it all happened so fast. I love him more then anything in the world and he makes me so happy; but it's like I waited so long to meet this little boy and the day he came was the best day of my life and it's already over. Seeing how he's changed in just a week and seeing how fast it's all gone by just really makes me break down. I love when babies are this little and he's going to grow so much with the blink of an eye. Is this common or could this be a sign im going to suffer from postpartum depression? I know they say if it lasts longer then 2 weeks to seek help, but does anybody else have the same problem?