Make Block Constantly Damage Player on Touch?

I have a block where I want it to do damage to the player at a constant rate (like 5 damage a second). Basically, when the player is on the block, the block will remove 5 health from that player each second. I want it so that it will still do damage to the player at a constant rate regardless of whether or not the player is standing still. I would also want the player to be slowed down when the player is on it. How would I do it? Here's what I have so far:

local CollectionService = game:GetService("CollectionService")
local part = CollectionService:GetTagged("DamagePart")

for _, TaggedPart in pairs(part) do
	local onblock = false
	function onTouched(hit)
		if onblock == false then
			onblock = true
			local h = hit.Parent:findFirstChild("Humanoid")
			h.WalkSpeed = 8
			while onblock == true do 
				h.Health = h.Health - 5
				wait(1)
			end
			onblock = false
		end
	end

	function stopdamage(hit)
		onblock = false
		hit.Parent:findFirstChild("Humanoid").WalkSpeed = 16
	end
	TaggedPart.Touched:Connect(onTouched)
	TaggedPart.TouchEnded:Connect(stopdamage)
end

This is quite buggy and does inconsistent damage. It also will sometimes not do damage when the player is standing still. If you could tell me what I did wrong and paste a working code snippet in I would really appreciate it. Thanks for your help :)

Also while you're at it can you please answer this question for me too? scriptinghelpers.org/questions/115188/bullets-are-not-going-through-objects-without-collisions