what makes my brake pedal go to floor by its self

An external brake fluid leak or an internal leak in the master cylinder. Have you checked the brake fluid level?

Yes I have and even changed the master cylinder and checked for thru out whole system

Would be really helpful to have all these details right away so we don't waste time getting to the solution. Why did you change the master cylinder? Was that to try to solve the low pedal or did the low pedal start after that? Did you bench bleed it or just throw it on and expect it to work? How did you bleed the system? Have you checked the rear brakes for a rusted adjuster cable?