I just replaced my iphone 3g screen & everything works fine except for the touch screen. How do I fix it?

I'm not sure but I think it might be the digitizer OR me hooking up the numbers 1,2, and 3 to the iPhone. I tried over and over again but it seems that 1 and 2 aren't "snapping" into place. I'm not sure if its suppose to but I also tried to use electrical tape to secure those 2 but nothing has worked. When I turned my iphone on calls go through and all my bars and signal for internet are there. Again its just the touch screen that seems to be the problem. (top button and home button both work perfectly) Can someone please help me? Or any tips would be great.