Be fruitful and multiply?

Ok so this is a topic a friend of mine brought up, and we disagree on it so I thought I would see whatever everyone else thought. She brought up the subject of having children and how she believes that if we get married we do not have a choice to have children or not that it is a command from God to. The verse she used was Genesis 1:28a. "Be fuitful and multiply and fill the earth." God is talking to Adam and Eve here right after He created them. Now to me the reason He said this was because there was noone else on the earth so ofcourse Adam and Eve being the only ones there they would have to multiply. Now the only other time God says this to someone is Noah and his family after the Flood. Genesis 9:1 "Be fruitful and multiply, and fill the earth." God says it in the same way! He just wiped everyone out with the flood so there was noone else. God doesn't just say Be fruitful and multiply, He always says "Be fruitful and multiply, and FILL THE EARTH." so the only reason God says this is when there is noone else on the Earth and He needs them to fill it. Well if this were to apply to us then He is saying Be fruitful and fill the earth, but the earth is full already. Also nowhere is this mentioned in any of the Hebrew laws or anywhere else in the bible. So you think if it were a command to EVERYONE then it would be mentioned throughout the bible. So my view is that you are not required to have children if you get married. Children are wonderful don't get me wrong, I love them! but I do not feel it is a command from God to reproduce. so tell me what you think.