Ay common yan sa second trimester, sis! The baby's taking up space na kaya ang diaphragm mo ay pushed up, making it harder to breathe, lalo na pag nakatayo ka or moving around. Marami sa amin na preggy experienced the same thing, and honestly it gets better once mag-deliver ka, pero for now try to slow down, rest often, at pag sobrang shortness of breath o may chest pain, best check with your OB agad para sure lang.