Formal:
* I just wanted to make sure.
* I wanted to double-check.
* I wanted to confirm.
Informal:
* I just wanted to be sure.
* I just wanted to check.
* I just wanted to see.
Más coloquial:
* Just wanted to make sure I wasn't missing anything.
* Just wanted to be on the safe side.
La mejor opción dependerá de la situación específica.