[carthinain]

in my bathroom i have a fixture that has 3 lights, i just pulled out the lightswitch (it's a old motion sensor), it has 2 black( one of wich has a black wire attatched to it), 3 white wires, and 3 grounding cables( they are twisted and clamped together. im trying to put them all on 1 switch

 

[TarheelTerp]

it has 2 black, ... 3 white wires ...
and 3 grounding cables (they are twisted and clamped together.

im trying to put them all on 1 switch

Whatever wires may be attached to or coming out of the old switch...
You need to identify the several cables coming into the box.
-what wires are in each cable, where it's from and where it goes.

Typically... that will be one "14/2" feeding power in,
and another 14/2 taking that power up to the light.
That's a total of two white wires and two black wires and two bare ground wires.

Often there is also a third cable involved...
which takes the (unswitched) feed power to another fixture.
That's three white wires and three black wires and three bare ground wires.

What do YOU have?

 

[carthinain]

Whatever wires may be attached to or coming out of the old switch...
You need to identify the several cables coming into the box.
-what wires are in each cable, where it's from and where it goes.

Typically... that will be one "14/2" feeding power in,
and another 14/2 taking that power up to the light.
That's a total of two white wires and two black wires and two bare ground wires.

Often there is also a third cable involved...
which takes the (unswitched) feed power to another fixture.
That's three white wires and three black wires and three bare ground wires.

What do YOU have?

i have 3 white wires, 3 black, and 3 ground wires.

 

[joed]

What was attached to the old switch?

 

[TarheelTerp]

i have 3 white wires, 3 black, and 3 ground wires.

And they are coming from 3 different cables?
Assuming so...

One "set" of these (from one of the 3 14/2 cables) is ALWAYS hot.
You'll need a meter or foolishness to learn which.

One "set" of these (from one of the 3 14/2 cables) goes to the lights.
You'll need a meter to check continuity to learn which.

The last set continues on to another room or fixture.

Once you learn which is which... get a new simple switch.
1) the whites will all go together under one wire nut.
2) the black going to the lights is put on one switch screw...
3) the other two blacks go to the other end of the switch
(one can be "back-stabbed" and one goes on the screw)