Well isnt that annoying if it is a warped bed! apart from trying the glass is there any other options? or maybe me and MrWetsnow are missing something that might be able to help us?

Do you have any kind of straight edge you can place across the bed to check if it is indeed warped, or even a laser pointer aimed across the surface might be able to show warping otherwise it may be something else....bent rails,loose mechanicals...

I've been trying to do it to how i understand is correct and ive put the extruder to each corner and ive been using some paper sliding underneath it and getting it even on each corner.... stick the extruder anywhere near the middle and the bed is too high and the paper wont slide underneath and if i drop the z then the corners arent correct again...

i ask this because ive been trying to print 3 or more of the same object at once, if i print just one in the middle its fine but if i print more it doesnt stick on the top or bottom prints but the middle print is fine.....could my bed be bowed in the middle perhaps or is this normal?