Is it too late for me to sue?
It appears that it is too late. The Texas statute of limitation for medical liability claims (malpractice) Civil Practice and Remedies Code section 74.251, which states:
Sec. 74.251. STATUTE OF LIMITATIONS ON HEALTH CARE LIABILITY CLAIMS. (a) Notwithstanding any other law and subject to Subsection (b), no health care liability claim may be commenced unless the action is filed within two years from the occurrence of the breach or tort or from the date the medical or health care treatment that is the subject of the claim or the hospitalization for which the claim is made is completed; provided that, minors under the age of 12 years shall have until their 14th birthday in which to file, or have filed on their behalf, the claim. Except as herein provided this section applies to all persons regardless of minority or other legal disability.
(b) A claimant must bring a health care liability claim not later than 10 years after the date of the act or omission that gives rise to the claim. This subsection is intended as a statute of repose so that all claims must be brought within 10 years or they are time barred.
So the rule is that you must bring suit within two years of when the act of malpractice occurred or in some cases two years from the end of the entire course of treatment in which the malpractice occurred. Here, UA tests were done 4 years ago and the entire course of treatment for the pregnancy and birth likely was concluded well before two years ago. In that case the statute of limitations is expired and you could not successfully sue now for it.
Even if you could sue, what damages (beyond some aggravation and the need to swap providers) did you suffer from the bad test results? If you didn’t suffer much in damages it would not be worth bringing the lawsuit anyway as you only win money to compensate for the harm you suffered from the malpractice.