Your GFR, which is the rate your kidneys are filtering your blood, dropped from 24 to 15. So, of course your toxins in your blood will be higher and less in your urine. Your blood is not getting cleaned. Your are on a "low protein diet," no doubt, so your protein will be less in your urine.
Yes, your kidneys are failing. You may still produce urine which is mostly water. That is lucky. Once you start dialysis you may stop producing urine all together and then you are very restricted on how much you can drink between dialysis sessions. If you still produce "some" urine you are allowed to drink "some" more fluid.
You will probably go on dialysis when your GFR drops to 10. Unless you start feeling sick before then. Make sure if you are feeling nauseated and really exhausted to call your doctor.
Best of luck.