The antonyms for the word "am untruthful" would be "am honest" or "am truthful." Being honest means telling the truth, without any intention to deceive or betray. It is a highly valued trait, and people often admire those who are honest, even when the truth is difficult to hear. On the other hand, being untruthful means lying or being deceitful, which is often frowned upon in society. Therefore, it is important to cultivate an honest nature and speak the truth, even if it is uncomfortable at times. By doing so, you earn the trust and respect of others and build relationships based on trust and integrity.