If a mother says you’re the father and you’re not sure, and you haven’t signed an Acknowledgment of Paternity, either she, the state, or the child can file suit to establish paternity.
Take this seriously: if you don’t show up for a paternity hearing after being summoned, a Texas court can issue a warrant for your arrest, or simply declare you the legal father by default — including a child support order — without your input. Request genetic testing as early in the process as possible to resolve the question definitively.