Does Painless White Patches On The Tongue Indicate Cancer?

Hi, I have 3 white patches on tongue without any pain. It will complete more than one month without any changes. I sew 2 doctores all of them said do not be worry it will disappeared with time and they just give me mouth cleaner. I read a lot about white patches from the internet and i read thad could be sign of HIV or cancer if not removed easily. Now I'm worried and couldnt sleep .. is that possible!!