Can my marriage be null and void?

We married when I was 19years old and He was 18years old. Hindi po alam ng parents ko that we got married, and sa marriage contract namin, family ng husband ko lahat ng witnesses. We did not secure a license or anything, wala rin pong ceremony, asa car lang po ako non and then sinabi lang po sa akin na napirmahan na po yung marriage certificate.

Question:
1) Sa Certificate of Marriage na nakuha ko sa NSO, may License number po doon, pero during our marriage, wala po kaming kinuhang license. Does this mean our marriage was legal?

2) I am now, 23 and I want to annul my marriage, what can be the reason why I will be annulling our marriage?
(we lived together for 4 years)

3) My Father recently found out I got married, is there a chance that He can file a case against us, or against the witnesses or the persons that signed as my guardian?

4) I have an expired NBI clearance and Phil-Health that has the last name of my husband and I want to change them back to my maiden name, is it possible?

Thank You

1) it is presumed to be valid until there is a court decree declaring it to be annulled. if you can prove convincingly that the ceremony was conducted without a license then the marriage is void.

2) if you lived together after reaching the age of 21, then you cannot use the absence of parental consent to void your marriage.

3) did you fake their consent?

4) you can request them to do it but it will be unlikely they will accede.

Thank AttyLLL...Regarding number 3,,, We just told them that my parents are out of the country and said that the aunt of my husband was my guardian. Thank You

i do not believe there is anything that your father can file against you or your aunt