Echo during calls after screen replacement?

I managed to change the screen, but now my callers get an echo. I tried calling myself from a landline and I heard it too, then I turned on the speaker and got such an awful echo (this time on my side - as in I heard the other side echo through the speaker with distortion and high pitched noise) took it apart once more to see if I had missed something, couldnt find anything, put it back together and the echo is still there. anybody got any suggestions??