Zombies dont hurt me?

I’ve been playing Gmod for a long time and came across this problem.
When zombies attack me, i dont get damage, as if they just pass by me.
same thing goes for all melee type attacks eg. headcrab bites and melee attacks done by combine elites with rifles.
however, damage from weapons still apply, like shootings and bombs and the stun baton still hurt.
is it something i have to turn on and off?

Could be an addon interfering with NPC damage. List the addons you’ve got installed.

oh and if a metro cop runs too fast and stops into me, we both get stuck
i pretty much have too many addons. i’ll just go and do a clean up