Implantation Bleeding??

Aly
Hi ladies, 
I sometimes think reading to many post's on articles like this can send you crazy! I've read a lot about implantation bleeding. I'm 5.5 weeks now and haven't noticed any. This is my 1st pregnancy, so I'm wondering does it happy for all pregnancy's? And if I don't have it would that be an indicator something is wrong? Would love to hear your thoughts xxx