Tummy time

Kate
My baby is 8 weeks, he's gonna be 2 months on Sunday the 10th. And he doesn't really lift his head that much while he's on his tummy on his activity mat. But when he's elevated on me or my husband or with a pillow under his chest, he's okay. Should i be worried that he can't do it flat on his belly? I'm jealous of all the babies that can lol