3 weeks is nothing, you have plenty of time, be easy on yourself. I have 2 DD's, there is a big age gap between them, 14 years. With DD1 I had the rush of love, I remember it so clearly, it happened at 11am the morning after she was born. It was wonderful and amazing and I was just so in love with her.
However with DD2 it just did not happen. I looked after her and worried about her but I didn't feel that love for her. I felt very cheated in the beginning, I had experienced the "rush of love" with DD1 and because I didn't feel it with DD2 I felt guilty, it made me doubt if I really did love her, I felt it was very unfair too especially as I knew what it could be like.
However DD2 is 3 now and I just absolutely adore her so so much. I'm so proud of her and think she is amazing. I can't say I had an actual moment where I fell in love with her as such, it was more a gradual thing which grew and grew and grew and just keeps on growing :)
I also suffered from PND initially and got some good advice from a counsellor I saw. She said to just say "I love you" out loud to DD2. Initially I felt silly saying it but soon the emotions began to come through, I found that simply saying I love you to DD2 helped me.
It's obvious you love your son MorrisZapp, otherwise you wouldn't be worrying about it. Give yourself some time, you will definitely get there :) Take care x
PS. Have found this thread very uplifting, even now I can feel sad and guilty that I didn't have that rush of love with DD2 and reading other peoples experiences has made me feel ok that it was more gradual with her. Thanks everyone for sharing.