Aww, I get why you're worried! An arched back can be normal sometimes, like pag excited sila or stretching, pero kung madalas talaga at parang kung hindi siya comfortable, better to check with your pedia just to be sure, ate. A few of us moms noticed our babies do this pag gassy or uncomfortable pa lang, so sometimes it settles down once nag-burp o nag-poop na sila, pero walang masama sa quick consult para sa peace of mind mo.