Tummy time with 2m6d baby boy

What am I not doing it right? Everyone I know with their babies can do heads up with their neck and shoulder supporting by month 2. But my baby boy has no sign of showing strong arms. Every time I do tummy time with him, he either smash his face against the bedsheet searching for nipple or he just lay flat and giving up trying to lift up his head. 😔 I also tired with towel roll under his arms , around his chest area to support him too. No luck. He just lay flat, head facing sideways. It’s like he doesn’t know what he is suppose with his arms.