Sometimes i have situation when enemy just hit me and im like *wtf i have high AC he should not hit me*
So i check logs...
He don't roll 20
It was not Attack of opportunity
My immediate thought is that your character might have been flatfooted at that time.
If you're just standing around with an empty action queue, or if your character is under certain effects like paralyze, stun, entangle, you might be counted as 'flatfooted'. Also if your attacker is invisible to you because of blindness, stealth or invisibility, and you don't have the blind fight feat, you will also count as flatfooted against their attacks.
While flatfooted you lose all of your dexterity AC, all dodge AC, and all tumble AC. This isn't shown on the character sheet or paperdoll, it just doesn't take that AC into account when defending against attack rolls.