yea i think having a proper conversation about it. explain beforehand that there is to be no arguing etc, just listening and discussing each others point of view.
for example, i always wanted to start my family when i was 30. my DF wanted to start a family much sooner. until he sat me down and actually explained to me why, i didnt get it. it turned out, that he was afraid of being an "old" dad. he would be 37 by the time he had his first baby. (if i had it my way). and it really upset him.
so i compromised and we met half way.
so maybe he just doesnt get WHY you want 3 kids. i want 3 kids so that each child will always have a sibling to go to, even if they are fighting with the other. lol.
wishing you lots of luck hun.