I applied for an SSS Number several years ago, but I have forgotten it. Can I get another SSS number since I have not contributed anything to SSS under that number?


You should have only one SSS number.
Two or more SSS numbers will delay the processing of your benefits, or might even reduce the amount of your benefits.

What you should do first is to go to the nearest SSS branch with your IDs, and ask your SSS number.
Ask the guard or front desk officer for an SSS number verification slip, so you can fill it up, and then submit to the counter verifying SSS numbers.

Bring your birth certificate (xerox and original) in case it turns out you do not have an SSS number, so you can then apply for your SSS number.

If you find out you have 2 SSS numbers, cancel the second number -- the one which has no contributions. Have this second number cancelled by SSS.  Retain the first one -- the one with the contributions -- and use only this number.

Enroll in online SSS, so you can monitor your SSS records.