What issues were you experiencing that led you to decide to reinstall the operating system?
Failing a DST short test could mean that your hard drive is failing. It could also mean that the device drivers were not installed in the correct order after you reinstalled the operating system.
First and most important step at this point is to try to backup your important personal files to an external drive just to be safe.
When all you files are safely backed up, You can try reinstalling the OS again, then follow the driver installation order linked below.
Dell requires that, after a reinstall of the OS, device drivers be installed in a particular order for the system to work correctly.
Drivers installation help. http/www.dell.com/support/drivers/us/en/19/help
You can scan for and obtain the correct drivers for your system, using your service tag.