Ladies I need some advice. So my son is 11 weeks old he can support his own head. He will lay on me…

Ladies I need some advice. So my son is 11 weeks old he can support his own head. He will lay on me and left his head up and look around and if I sit him on his butt on my legs he will hold his own head up and look around or if I put him on his tummy in his boppy he will hold his own head up. well if I put him on his tummy on a pilet on the floor he barely lifts his head up he just fusses I put toys down there with him and I shake them and make them rattle but he barely lifts his head up idk what I'm doing wrong any suggestions