I can roll over form back to tummy!

The day before I turned 4 months old I learned how to roll from my back to my tummy. Once I get on my tummy I get mad because my arm is stuck or I can't go anywhere! Going back to my back is just too much work. Then when Mommy flips me over I flip right back to my tummy and get mad again. And YES! My hair is finally growing back!!!!