Ay, normal lang yan, mommy! Babies stretch and arch their backs a lot especially around 2-3 months kaya siguro yan ang nakikita mo, it's part of their development as they're discovering their bodies. A few of us mums noticed our babies did this a lot around that age, kaya don't worry too much, but if your baby seems uncomfortable or in pain, or if the stretching looks unusual, best to check with your pedia just to be sure, okay?