Why is my mobile showing zero internal storage?

I am using samsung galaxy y gts5360 model. i install lolypop 5.0 in it but now it shows zero internal storage. Now i can't install any apps. it take longer time while switching on the mobile. How can i get my internal storage back??
Please help anyone

Welcome to Android Central! I assume you rooted the phone and installed a custom ROM. Are you sure you did it correctly? What steps were you following?