I am not multiplexing anything.
how can you do that without any multiplexing

4X4 keypad = 16 pushbutton = 16 i/o
LCD = 6 i/o
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22 i/o on a 18 pins PIC ?!?

you must calculate:
4X4 keypad = 8 i/o
lcd = 6 i/o
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14 i/o... will work with a PIC16F628 that gives a max of 15 i/o

or maybe you're using a 4X4 matrix keyboard decoder like an 74C922... that's one of those i use instead of multiplexing stuff, bitshift and bla bla bla.

in this case you'll need
5 i/o for 74C922
6 for LCD
total of 11 wich is great too