You are playing this very innocent, but you already had a fake ID, didn't you, so you must have done this before and not got caught. In Texas the penalty and charges for using fake ID are worse than if you had just been caught drinking underage - because it shows that you planned beforehand to be served alcohol despite being underage.
possible charges:
What are the legal consequences of possessing a fake ID in Texas?
Under Texas state law, a person under 21 who is in possession of a fake driver’s license with intent to misrepresent one’s age is a Class C misdemeanor, punishable up to a $500 fine. If the altered driver’s license has a fake identity rather than just a fake age or was issued to someone else, the offense is a Class A misdemeanor with a potential $2,000 fine and up to 180 days in jail.
Possession of a driver's license that is fictitious or has been altered is a Class A misdemeanor. Class A misdemeanors have a possible punishment of one year in jail and a $4,000 fine. This law also applies to possession of more than one currently valid driver’s license. A driver's license can be suspended for one year for fake ID and DWI
The other potential charge is for tampering with a government document, which can be a felony. This charge might be brought if a driver's license is altered in some way -- eg date of birth is changed.