Hello
What you are actually describing is; Depersonalization/Derealization disorder.
A person can have it as a disorder on it's own, or as part of other mental health condition such as panic disorder/depression/bipolar disorder.
I have experienced symptoms of DP which have been related to other problems I have, and I know how horrible it can be.
Firstly let me say this: you are not going mad in any way and can get better! Also, you are most certainly not alone.
When I first had symptoms of DP disorder, I thought I'd lost my mind. That thought in turn let to greater anxiety/panic, and had a snowball affect.
There are many forums dedicated solely to DP disorder, which you may want to visit for tips on recovery, speak with other people about it, and also it can help just not to feel alone.
Different methods will help different people. For me, accepting the symptoms and trying not to fight them helped me get better from it, along with several other self-help measures such as eating well, exercising, and just trying not to let it take completely over my life.
I wish you all the luck in the world getting better!