Honestly I think you need to do more water changes and please get the water tested. Without knowing whats happening in your tank, its hard to find a diagnosis, but I suspect you have ammonia poisoning going on in there, but cant be certain without water test results.
Do a 50% water change immediately, get the water tested, post the results here and we can take it from there.
Do a 50% water change immediately, get the water tested, post the results here and we can take it from there.