Does walking up and down stairs count as required daily exercise?

[The Lil Mama Omen]

for first period I walk up 2 sets of stairs to my locker then I walk down 3 because my class is in the basement
for 2nd period walk up 2 sets of stairs
for 3rd period I walk up 1 floor
for 4th period I walk down 3 floors then up one for lunch then back down
for 5th period I walk up 2
for 6th period I usually skip and me and my friends walk around the town to stores and stuff or a high school friend that's skiping will drop us off ( I got a A in that class)
for 7th period I walk down one floor then up 3 after school to my locker

I sometimes got a heavy backpack

I'm 21 weeks pregnant with twins do I still need to walk for at least an hour after school