Secure Erase won't do much if the SSD hasn't been used a lot already.
Make sure you have the latest FIRMWARE update.
*I'm not quite certain why you are reinstalling Windows. Unless you have an issue like a virus or you're installing a new version of Windows I don't see the point.
FYI, are you aware that Windows has a limited number of re-activations. Regardless of whether you reinstall Windows, make sure to create occasional backup Images using Acronis True Image. Free version available if a local or USB drive is WD or Seagate.
So in the future if you want to do a clean "install" you can simply RESTORE not reinstall. Always keep the backup you make after a fresh installation, Windows update and drivers, and ACTIVATION. Then, when you restore not only does it save time but you don't waste an Activation.
You should periodically delete your TEMP folder. Here's how:
1) reboot your computer
2) type %temp% into the Start Menu
3) Select All, then delete (skip anything it flags)
4) Empty the Recycle Bin