daughter of ex-military soldier

hi, I am a daughter of an ex-military soldier I was born outside the U.S. and out of wedlock. My mother lost contact with him when he came back to U.S. but when I reached 21 my mother found his where about and start communicating I was 25 when he sent his affidavit of paternity, I am married and live in the Philippines I never used his last name but my mom's. My mom already passed away and I have not seen my dad since birth, he's sick and could not come to visit me. Am I entitled to my U.S. citizenship? My dad is an American by birth.