Starterkit buttons dont fit the breadboard?

So i bought the arduino complete starter kit, with all the resistors led's and other components. In the verry first steps of the book your asked to put a button cross the center of the board. What cought my eye is that everytime i place a button on that locations it dosent make a verry good contact, the pins of the buttons look like there to short. So i started to test this with a little script to actually see whats going on. And yeah i was right, if i look up in the monitor the values i get are not constant (even if not pressing or even touching the button), it keeps swinging from 1 to 0 at random for random periods of time.

To give you guys a idea, here is the buttons i got in the kit
http://store.arduino.cc/eu/index.php?main_page=product_info&cPath=6_33&products_id=183

And this is the breadboard i got. (messurements should be the same onley exept for 840 pins my breadboard is about half the length)
http://store.arduino.cc/eu/index.php?main_page=product_info&cPath=6_32&products_id=25

Here is the code i use to read it out (with 2 buttons 1 reading) i was messing around abit and halfway i looked up a button reading for the monitor. Its partly dutch so knop = button

int knop1 = 2; //toewijzen knop1
int knop2 = 3; //toewijzen knop2

void setup(){
  Serial.begin(9600); //port geopent
  pinMode (2,INPUT);
  pinMode (3,INPUT);
}
void loop(){
  int buttonState = digitalRead(2);
  Serial.println(buttonState);
  delay(100);
  knop1 = digitalRead(2); //lezing knop 1
  knop2 = digitalRead(3); //lezing knop 2

Hope somebody could help me out here and give me some advice cause its pritty annoying with buttons falling out of my breadboard all the time. Ty for reading