Loading Screen not working

I am making a program to connect to tny.cz (like pastebin) using the http API. But the reason I'm asking about this is my loading screen. When I start the program, the loading screen flashes. I want the loading circle to sort of spin.

loading = 5
loadStage = 0
printActive = false
rednet.open("top")

function refreshLink()
	h = http.get("http://tny.cz/57e18bf1")
	y = h.readAll()
end

function checkPaste()
	sleep(0)
	if string.find(y,"ason") then
		 autoSpawner = true
	else
	autoSpawner = false
	end
end

function getPrintableVars()
	if autoSpawner == true then
		autoSpawnerPrint = "on"
		autoSpawnColor = colors.lime
	else
	autoSpawnerPrint = "off"
	autoSpawnColor = colors.red
	end
end

function printState()
	printActive = true
	term.clear()
	term.setCursorPos(1,1)
	term.setTextColor(autoSpawnColor)
	print("Auto Spawner is ".. autoSpawnerPrint)
	sleep(0)
	printActive = false
end

function loading()
   loading = 5
   repeat
		refreshLink()
		checkPaste()
		getPrintableVars()
		screenX, screenY = term.getSize()
		screenX = screenX/2
		screenY = screenY/2
		term.clear()
		term.setCursorPos(screenX-14,screenY-1)
		term.setTextColor(colors.yellow)
		print("InternetCraft Version Beta 1.0")
		term.setCursorPos(screenX-3,screenY)
		.setTextColor(colors.red)
		print("Loading...")
		stage()
		loadingCircle()
		loading = loading - 1
	until loading == 0
end

function stage()
	sleep(0)
	loadStage = loadStage + 1
	if loadStage == 5 then
		loadStage = 1
	end
	loadColor1 = colors.white
	loadColor2 = colors.white
	loadColor3 = colors.white
	loadColor4 = colors.white
	if loadStage == 1 then
		loadColor1 = colors.gray
		elseif loadStage == 2 then
		loadColor2 = colors.gray
		elseif loadStage == 3 then
		loadColor3 = colors.gray
		elseif loadStage == 4 then
		loadColor4 = colors.gray
	end
end

function loadingCircle()
	stage()
	term.setBackgroundColor(loadColor1)
	term.setCursorPos(screenX-1,screenY+2)
	print(" ")
	term.setBackgroundColor(loadColor2)
	term.setCursorPos(screenX+1,screenY+2)
	print(" ")
	term.setBackgroundColor(loadColor4)
	term.setCursorPos(screenX-1,screenY+4)
	print(" ")
	term.setBackgroundColor(loadColor3)
	term.setCursorPos(screenX+1,screenY+4)
	print(" ")
	term.setBackgroundColor(colors.black)
end

loading()

while true do
	if loading == 0 then
		checkPaste()
		getPrintableVars()
		sleep(1)
		refreshLink()
			if printActive == false then
				printState()
			end
	  end
end

Long story short, executing code takes time. The more operations you have your script perform in between clearing the screen and getting your page re-drawn, the more time the screen will spend blank. This leads to a noticeable "flash" effect.

I get the impression that all you really need to do is get rid of the sleep(0) in your stage() function. sleep works by rigging up a timer and waiting for it to expire - the minimum timer duration is a twentieth of a second (or one MineCraft server tick).

I'm not sure why you're calling stage() directly before loadingCircle(), then calling it again first thing once loadingCircle() starts. Together, that adds up to a tenth of a second delay.

If you must sleep, do so directly before clearing the screen.