Can't fell my placenta.

Natalie • 1 miscarriage , & now pregnant again with my rainbow baby 12-21-2015 ♥
I'm 13 wks 5 days and I can't feel my placenta , and everywhere I read people say they should be able to feel it at 12 weeks , I haven't had an ultrasound since 7 weeks , could my baby not be growing right or I just can't feel it yet ?