when i turn the switch to on, it goes on. but when i put it on the door switch and open my doors, it doesnt turn on. any thing i should check?

 

how long has this been happening?
Does the door switch thing on the front door jamb work?

 

check the pin/push in switch towards the front of the door jamb, may be sticking and not popping back out when the door is opened

looks sonmething like this:

 

I've had a door switch get dirty or corroded before. The quick fix for a little while is to press it in with your finger and then slide your finger off letting the switch snap back. Do that a few times and if it still doesn't work it may be too dirty or broken. Does this happen with both doors or just one?

 

also, check for broken wires and corroded connections behind the fuse box and on the door switch. my truck rusted through the back of the wheel well/front corners of cab resulting in the need to replace both the ECU and fuse box including pigtails.