Toilet constantly running !!?

When i flush toilet it constantly runs throughout the day..i flushed it this morning and its still going now and its 9.30 pm !!
We have tried to adjust the flow and worked for a bit but not for long..concerned as it cant be good this happening. The cistern is really low with water...its a toilet with a flush button in the centre of the lid of the cistern not with a normal handle.
for the mean time what i have ended up doing is holding something down to make the water in the cistern to come up to the line on the inside of the cistern but if i was able to do that manually myself does that not mean that something to do with the waterflow is broken or not working properly ??!!