Invincible for some reason, God Mode isn't on...

For some reason, I don’t take fall damage, I can’t hurt myself, NPC’s can’t hurt me, props can’t hurt me, and nothing else can hurt me. God mode is off. Trigger_hurts don’t hurt me. I can’t even drown underwater (it makes the damage noise but I lose no health). Any clue what the problem is?

Your playing Gmod

That’s not helpful. Why reply?
Anyway, have you checked that you have “God mode” off from the Singleplayer Sandbox menu?

Yes. God is off.

Did you install an admin mod?

sbox_godmode should be 0. If it’s on 1, thats your problem.