Why don't the edges of the screen read easily?

[thekingofnom]

edges of the screen do not read easily

I recently bought an M8 from someone( not able to get refund fyi) and i noticed that the P and Q keys were hard to press. I recalibrated and it began to work a little better. Later when i tried to reach the options tab in the upper right-hand Corner, i was unable to do so. Do i need a new digitizer , or is this a software problem?

P.S.

if i need to change a digitizer , I need tips on how to removes a jammed sd card slot....