I have a 2 year old acoustic guitar . Over the period of time there's a huge gap that has appeared between the higher frets and the strings. What has caused this gap? and How do i fix this.
This distance is known as the "action".
Three things affect the action.
All of these can be adjusted, but it's really a job for a professional, or an expert hobbyist.
If you want to try adjusting your truss rod yourself, read up on it first and be very careful (no more than 1/8 turn before re-measuring).
If you want to be confident of a decent job, go to a good guitar tech.
The fact that the gap at high frets is increasing would make me think of a bend in the neck or the front of the body of the guitar first. Can you check to see if the neck is true and straight?
If the neck is bent you may be able to adjust it if it has a truss rod, but if it doesn't then your only option is top take it to a luthier or guitar repair shop.
If you're lucky, you can adjust the truss rod and/or shave (and/or shim) the bridge.
If you're unlucky, your bridge is peeling off.
Take it to a shop to get looked at.