Hi. There is something wrong with my toilet. Initially I didn't notice, but as of recently every now and then the toilet starts making sounds. When I flush it the sound goes away. Upon a little inspection I noticed that when I took the back cover off the toilet, water started filling up. As it reached the top the noise continued and the water kept running. Once I flushed, the water went down and the noise stopped as well for a few moments and then started running up again. What do I do? :( I have a feeling my water bill is going to run up like crazy just because the water in the toilet won't stop running. Please help!