In the shower the water is hot or cold there no warm I want to know if there is something I can install to regulate the temp. its like one cancels out the other

What's the brand and model of your shower valve? Back to you, Tom

Yes, please let us know the brand of your shower valve. The shower valve should be all you need to control the temp. Sounds like you may have a defective valve or internal parts (cartridge, etc) Is this a new install, or has it always been this way?

It's a moen its always been like this that's why I changed it it is a new install

If it is a moen, it should be as simple as changing out the cartridge.