So, you have ich and you have put (right) medicine into your tank? right? What medicine are you using?
4 days isn't enough. You must use medicine correctly (read manual). Increasing temperature couple degrees effects on ich lifetime (makes it shorter). What kind of fishes you have? Can you increase temperature? Remember to use some airpump or lift your filter higher (breaking water surface) that water is well oxygenated.
Ich lifetime is approximately 14-21 days. So after you have medicated tank and after you don't see ich (white dots), you still need to keep this tank medicated at least one week so that all spores will be destroyed.
E.g. if you use Tetras medicine (contraick): Increase temp. about couple degrees, be sure water is oxygenated well. First you put medicine into your tank (and lights off). Then after 5 days you should use carbon to take medicine away. After that, you medicate again... And finally when you don't see any white dots, keep medicine in your tank still about 1 week. Medicine doesn't effect on parasite, it effects on spores which are in water finding hosts. Finally use carbon to filter medicine away.