OP, just an FYI your not looking for live current... you're looking voltage. That's what the tester is "testing" for.

You should probably hire an electrician. Unless you have a multimeter and know how to use it safely.. If you want to DYI then pay the electrician to troubleshoot and tell you what needs to be done i.e. run new romex.. then you can do it on your own dime. You also just might have a bad switch somewhere. Just had one fail OPEN two days ago... pretty common.

Whatever switches you flip - apply different amounts of pressure with your hand and actuate the switch OFF to ON and maintain pressure while ON. You may be able to get it to work for when applying force to the switch - however - when using this method it's best to have some type of load connected to your wires, such as a desk lamp, and a second set of eyes watching the lamp to see if it flickers or comes on while your flipping switches.... it'll take some time.. but it's an option... of course an option after you test for voltage with all switches ON in the house... and then test again with all switches OFF in the house... just in case. Good luck