Now the variable interest rate is very low. So people can change to bigger house easily. You could do that too. You do not necessarily need to pay more each month.
You could ask your bank to print out the amortazation Schedule, to show each payment how much the interest, how much the principal at your 3 or 5 years trem, vdery clearly. 你看到别人住的大房子, 但是你并不知道里边的事儿, 也许比你还痛苦, 见过有的人的大房新房, 但一屋的烂家具, 可惜了这副好皮囊.