OK...

Your settings look good, the ones that you have shown us... but here are some comments...

If you have problems, follow the instructions in the Datasheet.

They tell you that ANSEL should be set before ADCON1.

Also, if you are setting an entire Register using the Binary notation %, and the Register is eight bits wide, then you really should be setting all eight bits... ANSEL=%01010100 and not just seven bits.

You've not shown us your setting of ADCON0.

Have you also checked that your RA4/AN4 pin is not shorted out against any other pin or part of your circuit? Measure the Resistance between that pin and 0v, then unplug the PIC and measure it again on the socket. This way you will determine whether the excessive loading is internal to the PIC (indicating a possible setting error or other problem with the PIC), of if it is external on your PCB or breadboard layout.

Finally, beware of settings like...

OPTION_REG = %00000000 'weak pullups enable

That does a lot MORE than just set weak pull-up's.

OPTION_REG.7=0 ' Set weak Pull-up's ONLY (leave the other settings alone!)

Take a look at the OPTION REG in the Datasheet to see what I mean.